And thus in a nutshell describes the moral hazard of such programs. It's just another situation of balancing a program for those in truly in need and those trying to take advantage of the system. Very difficult to define boundaries.
Overall, I'd guess there are probably more salaried freeloaders than homeless freeloaders, and they make a lot more! There are places where you could do pretty much nothing in the bowels of some huge firm for 5 years and nobody would notice. And it's even easier if you do at least some work; I know plenty of people with office jobs who probably average 5 hours a week of genuine work. Of course, you might ask why homeless people don't just go get those cushy office jobs, which is an interesting/complicated question (they aren't really jobs you can apply for directly, are usually only available past a certain level of formal credential, require good bluffing, and require a certain amount of formal reliability, like showing up to work on time [even if you don't do anything there]).