A Montgomery County house hunter in 1971 could find a pleasant five-bedroom home in Potomac for $45,000. Late next spring, the same money in that county will buy a mobile home -- a nice one, to be sure, on a landscaped lot -- but a mobile home nonetheless, some 20 miles north of Washington.

And there already have been more inquiries than there are going to be trailers.

In an area where housing prices have almost doubled in five years and where the cost of a house is pushing $100,000, the prospect of a $35,000 to $45,000 mobile home in a carefully designed setting in prestigious Montgomery county obviously strikes a number of people as a good deal.

"We've gotten hundreds and hundreds of calls," said Maurice H. Berk, one of the developers of Wexford, the county's first officially blessed mobile home development.

Last week, after a three-year planning process. Wexford cleared its final government hurdle when the WSSC granted sewer allocations for 150 units in the trailer subdivision. Eventually, Berk said, the subdivision will consist of 386 immobilized mobile homes on a 100-acre site near Germantown.

According to Berk, the "mobile home community," as its developers call it, will look as little as possible like a traditional trailer park, something that the county planning board and other preserves of Montgomery County's wealthy image insisted upon.

"We're not going to call it a trailer park. We think it's going to be a community of homes," said Berk, whose intentions are to make Wexford indistinguishable from conventional "stick-built" suburbs.

The development will include a community area with a swimming pool and small clubhouse.

The county planning board, which turned down the project in 1976, approved it last summer in response to growing concern about how to provide low- and moderate-income housing in the area.

"The only affordable unsubsidized single family housing available in the United States is mobile homes -- and that's not available in Montgomery County," said county council housing specialist Peg McRory recently.

The number of mobile homes in the metropolitan area increased from about 2,700 to about 6,200 between 1960 and 1970. In this decade, however, construction of new parks has come to a near standstill as zoning restrictions grew tighter.

Montgomery County's first ordinance formally allowing mobile home development was adopted in 1974. Wexford, when it opens, will be the first subdivision built under that ordinance, although there are five older trailer parks. There are no mobile home developments in the District. Prince George's County now discourages their construction, according to planners there.

In Fairfax County, there is no vacant land zoned for mobile home development. However, the county board of supervisors in Fairfax has appointed a task force to look at the issue of mobile homes to determine if such housing may be the answer to the need for low- and moderate-cost housing there.

"In terms of the industry, the metropolitan area is no hotbed," said Jack Wynn, spokesman for the Manufactured Home Association. He said the industry is watching the development of Wexford with interest. "We feel it's one aspect of what our product can do to help the tens of thousands of people really priced out of the housing market," he said.