The company, which now has 80 units, mostly clustered in an area just south of Center City, has helped transform marginal blocks by rehabbing derelict properties and giving them the distinctly modern look that is Quad???s signature. ???From the start, we decided to try to find deals where we could build it the right way,??? says Kerr, who lives in a Quad property with a posse of fellow Fords (Jess