Buildings can present multiple problems. Bringing them up to code alone can require more than the effort is worth, before that the area/neighborhood is the primary hurdle. Unless the city councils change the zoning, disrupting the present inhabitants lives, it simply wont be possible. there are many examples of succsessful "gentrification' in the U.S. It takes govts, banks, anddevelopers working in concert and that takes years to accomplish.Quite amazing how in America, beautiful sturdy buildings are laying around abandoned. Why not convert them to living spaces like is often done in Europe?