Propelled by multi-billion-dollar sales and a 36 percent share of the nation's entire market for new homes, the "manufactured housing" industry -- the new euphemism for mobile homes -- has begun to shuck its tin-trailer image and move into middle-class suburbs and city neighborhoods.

It may, of course, be a few more years until mobile homes are found parked next to half-million-dollar estates or historic houses. Almost everywhere, they encounter resistance from homeowners fearful of eyesores in their neighborhoods and decline of their property values.

But the trend is unmistakable. Standard stick-built houses, especially at today's interest rates, have passed beyond affordability for all but a small slice of American home buyers. Manufactured houses can be built in one-third the time and half the cost of conventional homes.

Initially popular among itinerant workers of the 1930s, then for years the choice of last resort for military and construction camp workers, youth, retirees and the poor of all ages, mobile homes now seem destined to be the choice of the middle class.

Few problems are more likely to bedevil cities and towns than how to accommodate the new array of manufactured houses coming on the market. Opposition in many neighborhoods will continue. But today even the children of local establishment leaders are obliged to pick a mobile home as their first residence. Localities will no longer be able--politically or practically -- to segregate these structures into rental parks plunked down beside fumy freeways or industrial no-man's areas.

One problem is the immense variety of manufactured houses. The cheapest units are dreary-looking aluminum rectangles. But an increasing number are built with wooden window frames, full-size appliances and carpeting. The square footage in a "double-wide" mobile home is virtually the same as in the average conventional home. With the addition of a pitched roof, it may be virtually indistinguishable from a standard tract house.

Manufactured homes increasingly include such features as working fireplaces, cathedral ceilings, sunken bathtubs, bars, garages, patios -- even Jacuzzis and solar greenhouses. And mobile homes are becoming increasingly immobile. Only 3 to 4 percent are ever moved from their initial location.

Now coming on strong is the "modular home," which is factory-produced, transported in separate pieces to its site, and placed on a permanent foundation. Excluding land costs, prices can range up to $60,000 or $70,000--but still be substantially cheaper than a regular house, and thus help satisfy the pent-up, growing middle-class demand for homes.

Differentiating between all these forms in a local zoning code is a formidable--perhaps impossible -- task.

Nevertheless, cities and suburbs are under increasing pressure to open the gates to manufactured housing. Both the Council on Development Choices for the '80s, created during the Carter administration, and the Reagan administration's Commission on Housing have recommended equal treatment for manufactured and conventional housing.

Some states and localities already have moved in that direction, voluntarily abolishing all exclusionary barriers to mobile homes. Thurston County, Wash., made the leap in 1976, allowing mobile homes to be placed on any piece of private property where a conventional home normally would be permitted. Robert Goodhue, the county building department director, says there have been no major problems with the law. Occasionally owners of conventional homes complain when a manufactured home is put up on adjacent property, he said, but "with many of the newer mobile homes, you can't even tell the difference."

Indeed, defenders of manufactured housing argue that when mobile homes are permitted on private property the owners have an incentive to keep them up and improve them with a hope of increasing their resale value. The incentive is far less in a mobile-home rental park -- at least the lower-cost ones -- where a sloppy, second-class "trailer park" atmosphere all too often dominates.

In California, with perhaps the worst scarcity of affordable housing in the nation, state Housing Director Donald Terner has encouraged the state and local governments to overcome prejudices against mobile homes.

"Our objective is to have the mobile home go head-to-head with the stick-built home, to win where it can win and to be beat out when it can be beat out," Terner said.

Manufactured housing took a big step forward in California last year with state legislation prohibiting most local governments from barring mobile homes on foundations in single-family-dwelling areas. Like regular houses, said the state law, local zoning could set standards for roof and siding materials and roof overhang. There was a big loophole -- that communities could zone some areas for mobile homes, presumably barring them elsewhere. Still, the presumption that a mobile home could go practically anywhere was a major reversal in state law and a possible harbinger of things to come.

Oakland was ahead of the state law with an ordinance allowing manufactured homes anywhere in the city -- provided they have permanent foundations. A group named National Hybrid Housing Systems started placing attractive units on scattered sites around Oakland--all with high-pitched roofs and wood sidings. Mayor Lionel Wilson and other officials embraced the idea as a way to provide attractive and affordable housing for people of modest incomes, making available below-market mortgages under the city's municipal bond housing program.

None of these changes means the concerns many consumer groups have about mobile homes -- fire safety, wind safety, energy efficiency, defects ranging from leaky roofs to sagging floors -- can be dismissed. But the record is starting to show that quality manufactured housing can, and indeed will, play a big role in suburban, rural, even city housing -- and that it's the wise community that encourages the best of it.