Houses made out of Lego blocks? How about affordable homes built from 3D printers? Or temporary living spaces for the homeless made from plastic-like panels?

All of these ideas have moved off the drawing board and into the marketplace. Whether they gain any traction is another question. But they sure do look promising.

Take the blocks: They aren't really Lego bricks, but do resemble them. Lok-N-Blok, a company out of Paducah, Kentucky, introduced the composite, self-aligning, interlocking system last month at the National Association of Home Builders expo in Orlando.

The company had been waiting for the International (Building) Code Council to approve the product. Now that it has, the system is ready for market, said CEO Greg Siener to the 45,000 builders and professionals at the show.

Siener told me that the Lok-N-Blok system allows for quicker construction: about 50% to 60% faster than traditional wood framing. And since the blocks lock together, there is no need for specialized construction equipment or a highly trained labor force.

The blocks are made from a proprietary recyclable material that reduces waste at the job site. New blocks contain nearly 30% post-consumer materials and do not require mortar, cement or glue to be held together. The blocks are water-resistant, insect-resistant and bacteria- and mold-proof, the company says.

Siener said the response at the expo was "overwhelmingly positive," and that the display booth was "packed from open to close" every day.

Said one visitor: "This is too simple to be real."

The reception to Black Buffalo 3D's new production-ready printer, the show-stopping NEXCON 1G, was equally off the charts.

The NEXCON 1G has the ability to print buildings up to three stories, depending on roof design. The company says it can "print the frame of a 1,000 square-foot home in under 20 hours," and that it's so quiet, houses could "literally be printed overnight" without waking the neighbors.

Structures printed with the huge machine offer builders "a 70% reduction in materials costs, almost zero waste and up to an 80% reduction in labor costs and build time," per a press release.

"Our printer is a stronger, more sustainable and cost-effective way to build," said CEO Michael Woods. "Think of how much more the typical crew will be able to get done in the same amount of time."

Even though 3D printers have been in the news for years now, the NAHB show may have been the first time most visitors saw a machine up close. Feedback was "extremely positive and enthusiastic," Black Buffalo 3D Marketing Director Peter Cooperman told me.

Said one visitor: "I can't believe I'm watching a building being printed. This is amazing."

A month earlier, at the World of Concrete show in Las Vegas, Denmark-based company COBOD International demonstrated its version of the technology. COBOD calls it 3DCP, short for "3D concrete printing," and has sold about three dozen printers throughout the world. Here in the U.S., its printers have made houses in three different states so far.

One impressed onlooker at the Vegas show, Martin Carodine of Precise Concrete in Strawberry Plains, Tennessee, said his firm is looking forward to getting started with its own construction printing projects. "It was thrilling to see a printer live in action, and being able to have conversations face-to-face with the technology provider, a materials expert and an existing customer," he said.

Pallet Shelter's building system may not be as exciting: It's just seven panels, put together with everyday tools to form a completed unit of 64 square feet. But these tiny structures are helping to address a huge problem: homelessness.

According to the Department of Housing and Urban Development, on a single night last year, more than 326,000 people experienced sheltered homelessness -- meaning they were staying in emergency shelters or transitional housing. Of those, about 131,000 people were part of families with children. Both figures were lower than they'd been in 2020, but the number of "sheltered individuals with chronic patterns of homelessness" rose by 20%, says HUD.

Enter Pallet, an Everett, Washington, company launched in 2016 to address the need for disaster relief. Since then, it has built 20,000 "beds" for the homeless in some 20 states.

But the shelters are more than just beds. The easy-to-assemble units are insulated, heated and air conditioned, and have lockable doors to protect occupants and their belongings. Each shelter takes less than an hour to put together, and can be dismantled and put up again in another location. Within a few days, units can be built in villages of 20 units or more, with communal laundry, restrooms and 24-hour security. Meals, counseling and other services are provided by volunteer organizations such as the Salvation Army and veterans groups.

Some 80% of the Pallet workforce has experienced homelessness or incarceration. According to the company, the structures have made a world of difference to their inhabitants because having somewhere to sleep, wash their clothes and protect their valuables gives them the chance to "improve their lives dramatically."

Indeed, Pallet says most occupants move on to permanent housing within 90 to 120 days.

As for the company, a spokesman told me that these days, its "biggest challenge is keeping up with orders."

New affordability estimates show why so few houses are on the market: Owners who might want to sell may not be able to afford to buy another house. Even if they could find one.

Forget for a moment that there's a record low number of houses for sale, and just consider costs. Even using the profits from the sale of their current home, many sellers may not be able to afford another one.

According to the National Association of Home Builders, nearly 7 out of 10 households cannot afford a median-priced home in today's environment. That is, the incomes of 87.5 million families are not sufficient to qualify for financing under standard underwriting criteria.

Worse, for every $1,000 increase above the median price, some 118,000 more households are priced out, which is a major reason so many people are staying put.

The underwriting criterion the NAHB uses to determine affordability is that the sum of mortgage payments, property taxes, homeowner's and private mortgage insurance premiums (PITI) during the first year must be no more than 28% of the household's income. Key assumptions include a 10% down payment, a 30-year fixed-rate mortgage and an interest rate of 3.5%. (Note: At this writing, mortgage rates have already shot past 4%, which knocks many more people off the list of potential buyers.)

And, of course, there's more to it than simply selling one house and buying another. For one thing, there's the cost of selling -- an amount that can significantly eat away at the profits you'd hoped to use to buy your next place. The process of buying a house isn't cheap, either. And then there's the heady cost of moving.

All of these factor into the stay-or-go decision, so let's take a look at each one.

-- Selling. According to Bankrate, the cost to sell a house is roughly 10% of the selling price. So if you get $300,000 for your place, plan on $30,000 never finding its way into your pocket.

The largest part of that 10% -- typically 5% to 6% -- will be consumed by the agent who lists your house for sale. The rest is mostly nickel-and-dime stuff, which quickly adds up.

For example, even though today's buyers are overlooking many flaws, you'll still want to make some repairs. Otherwise, you'll leave more money on the table than it would have cost you to, say, fix a dripping faucet, repair a leaky roof or replace worn-out appliances. You might even want to have the place inspected to discover unknown problems that could quash your deal if not addressed.

If you plan to pay off your loan on the old house, you'll probably be hit with a few unexpected charges, such as prepaid interest and prorated property taxes based on the day you go to closing. You might even have to pay some of your buyer's closing costs.

-- Moving. Roughly half of all sellers use a professional mover, whether they are going across town or across the country, according to Zillow. HomeAdvisor reports that moving under 100 miles runs $80 to $100 per hour on average, which includes two movers and a truck. An interstate move will cost more, often in the thousands.

But that's an average of all moves, including those from apartments. Moving from a house, which tends to be larger and hold more stuff, means you'll pay more. Moving from a four-bedroom house will take eight to 12 hours, HomeAdvisor estimates, at a cost in the range of $640 to $1,200.

The cost of moving out-of-state is based on two variables: weight and distance. A reputable mover will give you an estimate based on both. (For reference: HomeAdvisor reckons the goods inside a four-bedroom, 2,800 square-foot houses weigh a whopping 20,500 pounds.) Obviously, the more you take with you and the farther you go, the higher the price.

Of course, you can call on friends and relatives to help you move, but you still have to rent a truck and buy the beer and pizza. You also might have to put your things in storage, which means not one move, but two. And you may have to pay for overnight accommodations.

-- Buying. Families moving up will want to maximize their down payments to keep their new mortgage payments as low as possible. Most, if not all, of your down payment will probably come from the proceeds of the sale of your old house. You may even have some money left over.

But if you are short on cash, you may be able to find financing for as little as 3% down. Loans from Veterans Affairs and the Department of Agriculture come with nothing down, but you have to be (or have been) in the military or moving to a rural location.

Another big consideration: closing costs. According to NerdWallet, these fees typically add up to 2% to 5% of the total price of the home, depending on location. So for that $300,000 house, expect to ante up anywhere from $6,000 to $15,000 in closing costs.

If you go for low-down-payment financing, you'll have to pay for mortgage insurance, which you may not have had to pay before. And if you are moving to a community run by a homeowners' association, you'll have to pay dues to keep the neighborhood in good condition. These two expenses don't usually require anything up front, but they are recurring costs to keep in mind. Also, moving to a larger place incurs higher property taxes and homeowner's insurance.

Hey, everything costs more when going big, even the heat and air conditioning. And if you get caught in the middle of two transactions -- selling your old house and buying the new one -- you could be saddled with two mortgage payments for a while.

Amid a white-hot housing market, the National Association of Realtors hit its highest membership count ever last year at nearly 1.6 million.

No doubt, some of the 101,000 folks who joined up are experienced agents and brokers who hadn't previously seen the need to associate with the giant trade group. But many of them are probably rookies who decided to cash in on an "easy money" market in which buyers were bidding against each other for the sparsest number of houses for sale in ages.

If you are considering listing your house with a new agent, though, you might want to think twice, even if she's your favorite relative. Yes, new agents have to start somewhere. But St. Paul, Minnesota, broker Teresa Boardman warns that having a real estate license "has nothing to do with selling a home."

Writing for Inman, an agent-centric news service, Boardman said, "It's quite possible to take the 90 hours of instruction and pass the test without having a clue as to how to write a purchase agreement or what to do with a listing contract."

Buyers, meanwhile, have to be careful whom they engage to help obtain financing. Regulators in 42 states have come down hard on 441 mortgage brokers who lied about completing their federally mandated continuing education courses. The guilty loan officers will pay about $1,000 in fines for each state in which they are licensed as punishment for skipping the required eight-hour classes, meant to enhance consumer protection and reduce fraud. They also must surrender their licenses for three months and take additional educational programs.

In Florida, both buyers and sellers should have their antennae up. The Sunshine State is one of 15 states where transactional brokerage is practiced, but it is the only one where that form of nonrepresentation is not disclosed. As a result, sellers are overpaying billions of dollars in commissions, a new Consumer Federation of America report maintains.

Transaction brokers are nothing more than facilitators with no obligation to either the seller or the buyer. It's not the dominant relationship between agents and consumers in the other 14 states, but it is in Florida.

Naples agent Chris Carter, who writes a blog about Florida real estate, calls transaction brokerage "the best-kept secret" in his state. And the CFA report says most real estate consumers doing business there don't question their agents' allegiance. They simply assume their agent is loyal to their interests.

Unless a savvy consumer asks exactly what the agent's role will be and opts for some other form of representation that cements the agent's role as a fiduciary who works only on their behalf, they are overpaying big-time, says CFA Senior Fellow Stephen Brobeck. Not only that, but they are exposed to significant risk related to the quality and price of the property.

Neither party to a sale in Florida can expect any advice from a transaction agent, Brobeck warns. Should such an agent help one or the other get a better deal, such as negotiating a better price, he or she would be breaking the law because those kinds of things are banned by state law.

Brobeck is calling on Florida lawmakers to require early and effective disclosure of all forms of representation and give consumers a choice. In the meantime, he advises consumers to demand much lower commissions because their agents have fewer legal responsibilities and less liability when they act as facilitators rather than fiduciaries.

Renters need to be on their toes, too. Like airlines and hotels that quote a low price online and then toss in junk fees when you go to check out, some apartment owners are doing the same. Not to pick on Florida, but here's an example from Tampa: An apartment's rent is listed at one price, but when you sign up, you discover you're also obligated to pay for pest control, cable, trash and even gate access.

Because many companies use junk fees to boost their bottom lines, the Consumer Financial Protection Bureau is starting to look into them. In the mortgage space, the federal watchdog agency says add-ons not only cost borrowers thousands in application fees and closing costs, but also can act as a barrier to ownership.

Beyond that, the CFPB says that borrowers are sometimes "forced to pay fees for making payments over the phone or online, or even for the servicer's bill pay service." And those who struggle to make their house payments often find it tough to catch up "due to the snowballing of a plethora of fees" related to their delinquencies.

Still, undisclosed charges like these don't rise to the despicable level of the unethical landlords who took money under the Paycheck Protection Program and then evicted hundreds of tenants.

The program was designed to allow companies to keep workers employed when their revenues were slammed during the pandemic -- like apartment owners, who took a big hit because their tenants couldn't make rent.

Unlike the CARES Act, which called for a higher level of protection for tenants in properties receiving a range of federal subsidies, PPP did not bar landlords from filing evictions. But from a broad perspective, it is rather contradictory that it supported companies that engaged in behavior that is at odds with federal humanitarian policies, say Elizabeth Strom and Denise Ghartey.

Writing in a recent edition of community development publication Shelterforce, Strom and Ghartey -- a University of South Florida professor and an attorney with the Community Justice Project, respectively -- said they found 95 landlords in three urban Florida counties (Miami-Dade, Hillsborough and Orange) who received some form of federal aid but still filed hundreds of evictions while state or federal moratoriums were in effect.

"Even when tenants filed court answers noting the protections of the CDC moratorium, the landlords featured here were likely to push ahead," they wrote. These very same landlords took millions in federal emergency aid.