Groton — The Town Council on Tuesday approved a tax stabilization agreement with an affordable-housing developer that plans to buy and upgrade Branford Manor, a 442-unit federally subsidized housing development.

Related Affordable, a subsidiary of Related Companies in New York City, is under contract to buy the development from owner Branford Manor Associates. The new company plans to invest $18.5 million to improve the housing complex in Groton City and build a community center.

The agreement lists how much the company would pay in property taxes for the next 20 years. Taxes would be paid twice a year and would increase by about 3 percent annually under the agreement.

Under the first year of the agreement, Related Affordable would pay $223,041 in taxes on July 1 and $148,694 on Jan. 1, 2018. In the last year of the agreement, the company would pay $391,104 in July 2036 and $260,736 in January 2037.