It's odd that we, as a society, will let people sleep in tents under bridges, or sleep in church parking lots, but let regulations and building codes keep them out of empty buildings? It’s actually a problem of being over-civilized. Here's what would be required to use vacant commercial space for temporary housing:

1) No liability. The owners of the building have to be totally insulated.

2) No regulations. Bureaucrats would have to be put on a short leash.

3) The place has to be run like an army barracks to provide a sense of order for chaotic lives.

4) It has to be a true charity, not a non-profit that profits the supposed rescuers.

5) Make it easy to donate to, including expired or homemade food.

These are all difficult but solvable issues, however, self-righteous, sanctimonious indignation seems to be the biggest stumbling block for providing shelter to people who really need it; the problem is who wants to be the one blamed for pictures of kids sleeping under Space Blankets on the bare tile floors of an abandoned shopping mall.