Substantial rehabilitation of the Sky Towers garden apartment units in Southeast will be started soon as the result of an unusual, $2.2 million construction-permanent loan made under a federal housing financing program.

Perpetual Federal Savings and Loan Association is making the 40-year, FHA-insured loan to the National Capital Housing Authority, which owns the foreclosed, partially vacated buildings, at an interest rate of under 7 percent. The lenders will br exempt from federal income taxes on money earned by the loan.

Walker & Dunlop, a downtown mortgage banking firm, represented NCHA and placed the loan with Perpetual for rehabilitating the 91 rental dwellings for low-to moderate-income families. Units will have one to six bedrooms. The rehabilitation plan also includes landscaping and the creation of tennis and basketball courts on the 4.3-acre property, which is in the 1000 block of Wahler Place SE near Wheeler Road.

Completion of the rehabilitation program is scheduled for a year from now, with initial occupancy of renovated dwellings likely to began at the end of this year.

After HUD tore down nine of Sky Towers' 19 buildings, tenants, successfully fought the razing of remaining buildings. The complex, constructed in the 1950, was fixed up in 1970 with FHA-insured financing and then foreclosed in 1972 by the Department of Housing and Urban Development, which urged the District's houing authority to purchase the project.