Brooklyn-based Infinity Properties has filed applications for a four-story, four-unit residential building at 16 Underhill Avenue, in Prospect Heights. The project will measure 5,513 square feet and its residential units should average 1,207 square feet apiece. The full-floor apartments will likely be condominiums. Gerald J. Caliendo’s Briarwood-based architecture firm is the architect of record. The 30-foot-wide, 2,427-square-foot property is vacant. The Clinton-Washington Avenues stop on the C train is two blocks away.