A number of elderly low-income tenants thought all was lost when their Northwest apartment building was put up for sale five months ago.

Instead of shrugging their shoulders and joining the legions of Washington's displaced poor, however, these tenants used MUSCLE -- Ministries United to Support Community Life Endeavors.

As a result, last week the tenant group purchased their 51-unit building at 1901-1907 15th St. NW for $550,000. They plan to spend $450,000 for its rehabilitation and conversion to a combination cooperative/rental complex.

MUSCLE, a nonprofit group based in Southwest Washington, provided technical assistance and helped the tenants benefit from a recent District housing law giving tenants the first right to purchase their apartment building when it goes up for sale.

"We might not have been able to buy our building if MUSCLE had not given us advice," said Burnett Johnson, president of the tenant association. She said one of the tenants heard about Muscle and asked the group to help.

Muscle negotiated a contract with the owner's representative, helped fight an anxious developer seeking to purchase the property, found a lender for the building's purchase and rehabilitation and then got the city to guarantee the loan, she said.

The group, which has six employes and a contract with the D.C. Department of Housing and Community Development, has helped other tenant groups as well. They include the 58-unit Tel Court Apartments at Half and O streets SW, the 68-unit Jeffrey Terrace Apartments, at 2430 Elvans Rd. SE, the 40-unit Imperial Apartments, at 1736 Columbia Rd. and the 34-unit 1727 R St. apartments, both in Northwest.

Alice Vetter, a housing consultant and director of MUSCLE, said the group, organized by a handful of clergymen, began in 1978 to help offset the dramatic displacement of Washington's poor.

"In a nutshell, we are a nonprofit developer," said Vetter, who explained that her organization only works with low-income tenant groups. She said MUSCLE has a joint contract with University Legal Services, a nonprofit law firm that provides legal aid to the tenant groups as well.

Last summer, MUSCLE helped residents at Tel Court Apartments purchase their building for $691,000. Leon Field, a spokesman for the tenant group said, "MUSCLE deserves a great deal of credit and so does University Legal Services."

It appears, however, that MUSCLE got off to a rough start with the Tel Court project. Field criticized the group saying he believed it should have been in closer touch with tenants during the bargaining process.

Vetter said Tel Court was MUSCLE's first project and that workers were unsure what their negotiations with lenders and government officials would achieve.

"A lot of those contacts with lenders in Tel Court's behalf were really just fishing expeditions," Vetter said. "Since the Tel Court experience our style has changed. We can now include tenants in every step of the way."

Other tenant groups, however, had no complaints about MUSCLE's work. Barbara Valentine, a spokeswoman for Jeffrey Terrace in Southeast -- now called the People's Cooperative Association -- said MUSCLE "assisted us in forming the cooperative and provided valuable information for us."

One resident at the 17th and R Street complex in Northwest, added that Vetter even supplied a $7,000 personal loan to help guarantee the tenant's deposit on a loan to purchase the complex.

Robert L. Moore, director of the D.C. Department of Housing and Community Development, said: "Their track record is not that long yet, but they have done a number of conversions."

The housing department plans to give MUSCLE responsibility for aiding tenants in a major portion of the District. Moore said the group, which has a year-long contract, will be given jurisdiction in half of the city to help tenants. The Metropolitan Washington Planning and Housing Association, which has done smaller housing conversions, will be in charge of helping tenants in the other half of the city.

Meanwhile, tenants at 1901-1907 15th St. NW celebrated last week at St. Paul and Augustine Church at 15th and V streets NW. Johnson, who said some of the tenants have lived in the apartment building since the turn of the century, said her group was determined not to be displaced. "We would have bought this building one way or another."