Like everyone else, homeless people tend to have ties to specific areas, and by the time you're homeless you tend not to have the capital required to move and restart someplace else.

Basically at what point do you decide you're "failing" (no moral valence intended) in one area in which you have a support network that you're willing to risk moving to a totally new area and starting over? At that point, do you have the resources required to do so successfully?