Dozens of Madison families living in subsidized housing are scrambling to find new homes as they face the possible closure of two apartment complexes. At least 15 of the 45 units of affordable housing at Tree Lane Apartments, on Madison’s west side, and 24 of 60 units of affordable housing at the east side’s Rethke Terrace Apartments are already vacant as tenants have moved out after the ownership group of both properties crumbled.