Open this weekend — Saturday, September 12, 12:00–2:00 p.m. and Sunday, September 13, 1:00–3:00 p.m. A rare three-family on Blue Hills Parkway, in the Milton Public Schools district, between the Neponset bike path and the Blue Hills Reservation. Mattapan Station, local buses, and the highway are a short hop; Tucker School is next door, Churchill’s is down the parkway, and trails and neighborhood parks are out the door. Three units: two three-bedrooms and one -bedroom. The first floor is vacant and opens to a large lower level — a natural owner’s suite with room for extra bedrooms and a bath. Units 2 and 3 are occupied, so you can live on one floor and keep income on the others. Hard to find this much flexibility in Milton, this close to the reservation and the T. Come through Saturday or Sunday and see it for yourself.