Owners of government-subsidized housing for the poor have scored a victory in Congress that would allow them to sell their buildings or raise rents at the end of expiring 20-year terms in which they agreed to keep their housing for use by low-income residents.

The House Banking, Finance and Urban Affairs Committee last week approved the provisions, which are part of omnibus housing legislation. The full House is expected to begin considering the measure next month.

Finding a way to preserve some of the estimated 360,000 low-income housing units that could be lost over the next decade is one of the most controversial shelter issues facing Congress this year. The Congressional Budget Office recently predicted that owners of more than two-thirds of these units will convert them to market-rate rentals or sell the buildings unless Congress passes new legislation to preserve them for low-income people.

Two decades ago owners of such government-subsidized housing were assured that they could charge market-rate rents at the end of the 20-year periods for which they agreed to keep the housing for low- and moderate-income residents. Now many of the owners are seeking to ensure that the agreements are not changed.

But housing advocacy groups argue that the loss of so much low-income housing could cause hardship and homelessness for the tenants, many of whom are elderly. These advocates are urging Congress to pass legislation that would keep the units available to the poor, but property owners say they have fulfilled their agreements with the government and should not have new obligations imposed on them.

Congress is facing this dilemma because of what one former federal housing official called a "blind spot about what would happen down the road" when several federal housing programs were created during the 1960s. The programs, needed to help people who had too much income to qualify for public housing but not enough money to pay market-rate rents, offered low interest rates on mortgages and other subsidies to property owners who agreed to keep rents affordable for at least 20 years.

When building owners began paying off their mortgages several years ago at the end of their 20-year obligations, Congress passed the Emergency Low Income Housing Preservation Act of 1987. This legislation will expire Sept. 30, and advocates say Congress will have to approve new measures if it wants to keep the housing within reach of the poor.

Critics said the House bill approved by the committee will not preserve enough of the low-income housing and will result in displacement for many tenants. The Senate's proposals closely track the current law and would preserve more low- and moderate-income housing, they said.

"Nobody has suggested that owners should not receive some fair and reasonable compensation" for renting to low- and moderate-income residents, said Barry Zigas, National Low-Income Housing Coalition president. "The problem is {the House bill} makes this a completely voluntary program on the part of owners" and because of "the great variety of owner motivations, it will undoubtedly lead to displacement of very low income tenants."

Zigas predicted that ultimately Congress will reject the provision favoring the building owners, which was introduced by Rep. Steve Bartlett (R-Tex.) as an amendment to the larger housing bill. The measure is "so far out of context of what Congress felt in the past was fair and equitable, that there will be less and less support for it as people look more closely at it."

A spokesman for the Department of Housing and Urban Development's Washington office said 64 apartment projects in the Washington area will become eligible for conversion within the next 10 years. Lynda Given, Prince George's County's housing and community development director, said about 20 of them are in her jurisdiction but that none of the owners of these buildings have said they want to convert their buildings.

Many of the properties throughout the country are a mix of low-, moderate- and market-rate rental units. One of these is Aspen Crossing, a 192-unit building in Wheaton, where tenants in 28 of the apartments have low and moderate incomes. Lothar Steschner, who lives with his family at Aspen Crossing, said the development "was a really nice neighborhood." Steschner and his family pay $753 a month for their market-rate unit and will be happy to stay at Aspen Crossing until they can find a house to buy, he said.

The House bill would allow owners to pay off their mortgages, raise rents or sell their buildings after giving the Department of Housing and Urban Development, local officials and the tenants two notices. Low-income tenants who were forced to move would have their relocation expenses paid for by the government.

If owners decide to continue renting to low- and moderate-income tenants, the government would increase the subsidies so rents could be raised. This obligation for low-income use would last another 20 years, compared with the Senate bill's requirement that the housing stay low-income for the life of the property.

The Senate's proposed legislation and current law requires owners to maintain the same mix of very low-, low- and moderate-income tenants living in their buildings when the current legislation was passed three years ago. But the House bill has no provisions to require that some of the housing be reserved for very low-income residents, who are those with incomes at 50 percent or lower of the median income in the community where they live. The median is the point at which incomes of half the population are lower and half are higher.

Eugene Ford, a Washington-area developer and head of the Institute for Responsible Housing Preservation, an organization of owners with expiring use restriction buildings, said he believes "there's a general misconception" that all property owners are waiting to convert their buildings to market-rate rentals.

"Our basic position is that you really have to deal with our rights ... but we accept the principle that the housing" has to be used for the tenants who are there now, he said.

Ford said he houses about 40,000 people in the 13,000 units his company has built since 1965.