The federal Department of Housing and Urban Development is preparing to sell the 396-unit Congress Park apartments in far Southeast to a private developer.

The 27-year-old complex that contains town houses, apartments and a shopping center currently is home for 146 moderate-income families. Many of these tenants fear that the sale of the project would force them to find other housing.

"If sold as is in that desirable area, there is no doubt that private developers will buy it and double or triple the rents," said Florence W. Roisman, an attorney representing some of the tenants who oppose the sale.

"Congress Park is a project we foreclosed on" the private owners nine years ago," said James Clay, director of the Washington area HUD office. "The department is not a landlord or real estate agency."

Since the department is interested in insuring mortgages on property and not in operating properties, "we must expeditiously get it out of our hands," Clay explained.

Before the department can actually offer for sale the complex located between Alabama Avenue, Mississippi Avenue and Wheeler Road SE, officials must determine whether to sell the apartments and shopping center in one package or each separately. Officials also must decide whether to offer the property at any price or set a minimum level for all bids.

These decisions will be based on "which way would bring the most money to the (HUD) secretary," one official said.

Congress Park is the second HUD-owned project in far Southeast that the department has attempted to sell in the last two years.

In 1975, U.S. District Judge Gerhard A. Gesell stopped the department from evicting low- and moderate-income tenants from the Sky Tower apartment complex on Wheeler Road. Gesell also ordered the federal agency to stop demolition of the buildings. HUD intended to tear down th buildings and sell the land to a private developer.

Late last year, HUD agreed to sell the remaining apartment buildings to the city government.

Jean Walker is one of several former Sky Tower tenants who moved to Congress Park.

"When I first heard about the sale of Congress Park, I panicked," she said yesterday. "I said, 'Oh God, I cannot go through this again if I can help it."

"It's too hard to get out and look for a place," she said, noting that she now has a comfortable four-bedroom, air-conditioned apartment with a washer and dryer at a rent of $198 a month. "You tell me where I can find another apartment like this for $198," she said.

The decision to sell the project comes at a time when the far Southeast is enjoying a renaissance in a single-family home ownership after almost 30 years as a dumping ground for apartments built for low- and moderate-income families by both the government and private developers.

Now developers are building town house projects through the area, priced for sale to young, middle-income families.

The Congress Park apartments were built in 1950 to meet the shortage of apartments for young families that developed after World War II.

The old Federal Housing Administration insured the mortgage on the project, which cost $7.2 million. But by the mid-1960s, the project was blighted by vandalism, crime and general deterioration. HUD foreclosed in December, 1968.

A year after the foreclosure, HUD began a three-year renovation program of 148 vacant apartments at a cost of $2.3 million, one official said. The department intended to renovate the entire project and then sell it, but it quickly became apparent that the renovation costs were prohibitive.

Currently there are 250 vacant apartments. Only two stores remain in the once-thriving shopping center - a delicatessen and a liquor store.