The Marin Housing Authority recently avoided having to spend $ 564,000 to buy back two below-market rate homes it oversees in the county. In August, the housing agency requested and received permission from the Marin County Board of Supervisors, which serves as its board, to repurchase a home at 6 Presidio Court in Corte Madera for $ 274,000, including $ 3,458 in anticipated closing expenses.