The 1,060-unit Queenstown garden apartment complex in Mount Rainier is scheduled to be sold for $10.5 million to a Washington developer who plans to rehabilitate the 33-year-old Prince George's County property and retain it as a moderate-income rental community.

Eugene Ford said that he and his Mid-City Financial Co. have a contract to purchase Queenstown from a partnership headed by the Henry Barron family.

Ford, a former mortgage banker who has been building apartments in Northeast and Southeast in recent years, said that the purchase is contingent on obtaining a 7 1/2 percent, FHA-insured Section 221(d)(4) loan to rehabilitate the property at a total cost of $24 million.

To allay fears of tenants, many of whom are senior citizens, Ford said he has no intention of converting the complex to condominium ownership and plans to keep rent increases within a 10 percent annual maximum. Ford said that rents for the one- and two-bedroom apartments now range from $250 to $350 amonth, including utility charges.

The 33-acre tract bordered by Chillum and Queen's Chapel roads is eligible for below-market financing through the Government National Morgage Associaion.

Ford said that the 150 brick buildings will be upgraded and made more energy-efficient.