Jon Gorey - Globe Correspondent

It’s notoriously tough to afford a home around Boston, a fact of life threatening not just new home buyers and low-income residents, but arguably the economic vitality of the region itself. Hungry for housing solutions, leaders are pressing for more low- and moderate-income units or to loosen local zoning restrictions on high-density, transit-oriented development.

But we might be overlooking — or even snubbing — one of the least expensive and most effective means of addressing our housing woes: mobile homes.

“Mobile homes are this country’s single largest source of unsubsidized affordable housing,’’ said Esther Sullivan, author of “Manufactured Insecurity: Mobile Home Parks and Americans’ Tenuous Right to Place’’ and an assistant professor of sociology at the University of Colorado, Denver. “They provide housing at an unmatched level of deep affordability.’’

With a median household income of $33,400, most manufactured home residents in the United States would qualify for subsidized housing — if there was enough available, which there isn’t. To bridge that gap, they’ve found an imperfect but mathematically viable workaround in the private sector. While the median price of a single-family home in Massachusetts was $423,250 in July — and at $398,950, the median-priced condo wasn’t much cheaper — the average manufactured home doesn’t even fetch six digits brand new.

Before we go any further, let’s define some terms. A manufactured home is essentially a mobile home built after 1976, when the Department of Housing and Urban Development established a nationwide building code to ensure all manufactured housing was constructed to new standards of safety, quality, and efficiency. “The HUD Code was the first preemptive national building code in the world,’’ said George “Mac’’ McCarthy, president and CEO of the Lincoln Institute of Land Policy in Cambridge. That means it supersedes all local building codes, making it possible to complete and inspect a home at the factory. “A lot of people act as if it’s a problematic housing stock, but that’s because they’re looking at stuff built before the HUD code,’’ McCarthy said.

Modular (sometimes called “pre-fab’’) homes are likewise factory built, but delivered in sections and then assembled on site. That means they share some efficiencies of off-site construction — there are no weather delays on the factory floor — but they’re still subject to local building codes. “The problem with modular is you can’t bring it to the site ready for occupancy, you have to leave the walls open so local inspectors can inspect the electrical and plumbing,’’ McCarthy said. “But you can still displace a lot of the construction cost, and you minimize waste.’’

What makes housing unaffordable in Boston, McCarthy said, isn’t just the high price of land — though that’s a very large part of it — it’s also the cost of local labor and construction. And that’s where the waste-reducing, assembly-line efficiency of manufactured housing yields big savings. The median site-built home in the Northeast cost $135.10 per square foot to build in 2017; a manufactured home averages just $50.42 per square foot, or less than half the price. McCarthy said a 1,600-square-foot single-family home can be produced in the $80,000 range, even with high-quality materials and Energy Star-rated efficiency. “There’s no way you could touch that with on-site construction,’’ he said.

Those numbers should grab the attention of sticker-shocked house hunters and affordable-housing advocates alike. But manufactured housing also faces a few mostly external obstacles.

The first is land ownership, or lack of it. About a third of manufactured home residents own their home but rent the land beneath it in a mobile home community. Most of these parks are run by private, profit-driven businesses, and Sullivan said it’s problematic to rely on them so heavily for our affordable housing. “In these parks, residents don’t own the land, and often they have equivalent or even fewer rights than an apartment renter. But their burden is so much greater — because if they’re evicted, they need to move both themselves and their homes,’’ she said.

Residents of such communities face three basic vulnerabilities, according to Paul Bradley, founder and president of ROC USA, a New Hampshire-based nonprofit that helps residents purchase their parks and operate them as co-ops. They can face steep and sudden rent hikes, Bradley said, particularly after a change in ownership; they’re also at the operator’s mercy when it comes to park maintenance and safety issues. But worst of all, they can be forced out of their homes if the park is sold to a developer. “If there’s a ‘higher and better use’ for the underlying land, like a Hampton Inn or a Home Depot, the risk is the community closes down and the homeowners are displaced,’’ Bradley said.

Mobile home communities, often zoned into nonresidential areas on the outskirts of town, are thus early victims of urban growth, Sullivan said. “They’re already on a large tract of land, and as cities have grown around them, they provide land that’s ripe for redevelopment from the perspective of the sheer size of it and the ease of disposing of these residents,’’ she said. And despite the name, mobile homes aren’t easily moved. The vast majority stay put after delivery, and Bradley said it can cost up to $15,000 to move a manufactured home, even across town.

“People walk around with a pit in their stomach thinking the rent will be raised or the community could be closed down,’’ Bradley said. “It’s a dark cloud.’’ That’s why the former executive at the New Hampshire Community Loan Fund founded ROC USA in 2008 — to help mobile home communities band together and buy the land beneath them, adding a sense of stability and control over their own destinies.

ROC USA recently helped the residents of Halifax Estates, a 55-and-over manufactured home community in Halifax, purchase their park. Resident and realtor Charlie Brine said rents went up by about $100 a month to cover the cost of financing and long-delayed maintenance, and that stung for some residents on fixed incomes. But for the most part, people understood and appreciated the long-term benefits of self-ownership.

Two units are on the market and both recently went under agreement. One, built in 1975, before the HUD Code took effect, was listed for $59,900. There are a couple of soft spots in the floors — something that happens in older mobile homes, Brine said. “Almost everyone’s patched a floor at some point,’’ he told me. A second unit — a 1976 double wide with a sunny front porch and roomy family room — was listed for $116,900. The monthly park fee of $593 includes water, sewer, taxes, trash pickup, and basic cable, and both homes come with driveways and a nice patch of grass in what feels like a modest suburban housing development. There’s a new one slated for delivery soon: a two-bedroom, two-bath home with a den and a gas fireplace for $213,375.

Here, though, we run into obstacle No. 2: financing. “It’s almost like buying a used car as far as paperwork; it’s pretty simple,’’ Brine said. And mobile homes on rented land tend to depreciate more like a car would, too. “They do depreciate quicker than a regular home, but when mobile homes are located on land the homeowner owns, they appreciate more on par with conventional homes,’’ Sullivan said.

Because manufactured homes evolved out of the travel trailer market decades ago, they’re still generally treated as personal property rather than real estate. That leaves many buyers stuck in the chattel loan market, where, compared with the federally backed mortgage industry, interest rates are higher, loan terms are shorter, and lenders are few. It can be difficult to finance a mobile home more than 20 years old, Bradley said, creating a kind of cliff for resale values. “It’s difficult to support housing values when there’s no market for financing,’’ he said.

And that’s a result of the third, and maybe biggest, hurdle: the stigma. While manufactured homes can be customized with graceful roof lines and high-end finishes like quartz counters and marble baths, their reputation as portable lodging for poor workers persists. “This is an affordable-housing solution that some cities and towns are willfully ignoring, and I think that speaks to the stigma of manufactured housing and the people who live there,’’ said Mike Bullard, communications manager at ROC USA.

“There’s nothing about this housing structure that makes people ‘trash,’ ’’ said Sullivan, who lived in two mobile home communities for over a year while researching her book. “In my own experiences, I found these places to be really vibrant, supportive communities of neighbors.’’ But the decades-old stigma against manufactured homes “is codified in law in the form of zoning and local planning ordinances,’’ she said.

“Some municipal zoning bylaws explicitly prohibit mobile homes,’’ said Olympia Bowker, an attorney at McGregor & Legere in Boston. Other towns discourage them in more subtle ways, such as minimum square footage requirements or by simply omitting them from town zoning maps or tables of uses. Because the HUD Code is universal, McCarthy said, communities can’t actually zone away manufactured homes — but that doesn’t stop them from trying.

One result of that stigma is that tiny houses — subjects of so much fascination and more than one HGTV show — are also prohibited from many communities. Perhaps owing to the popularity of tiny houses, though, the stigma against mobile homes shows signs of subsiding. In Oakland and Seattle, for example, developers have used manufactured housing as infill on small urban lots, stacking units on top of one another.

Sullivan knows mobile homes aren’t a cure-all for housing, but says they deserve to be part of a bigger solution. “Certainly we shouldn’t be getting rid of the affordable housing we already have by getting rid of trailer parks,’’ she said.

In Massachusetts, McCarthy sees plenty of opportunity for high-quality manufactured homes, including in old industrial lots along commuter rail routes. But the impact they have in addressing our affordable housing shortage may ultimately depend on how big a role we allow them to play. “We haven’t even gotten close to the potential of using manufactured housing as part of the solution to affordable housing,’’ he said.

Jon Gorey blogs about homes at HouseandHammer.com. Send comments to [email protected] . Follow him on Twitter at @jongorey. Subscribe to our free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp.