This may sound flippant but... Poor people who are not mentally ill often do exactly that. Even some drug addicts can sometimes get together to rent a place t

This may sound flippant but... Poor people who are not mentally ill often do exactly that. Even some drug addicts can sometimes get together to rent a place to crash. But we're talking about the severely mentally ill here. They are unable to band together. I imagine that this is sort of by definition... those who's mental illness illness is mild enough that they can help themselves by working together... just do it. The remaining are on the streets.