It would be better for all of us if the homeless had someplace to live. If we had the moral upbringing and the political will to solve this, here would be two beginnings:
First, travel trailers parked temporarily. There's almost an infinite supply of these, they are moderately fire resistant, and would be a real upgrade from tents. They should be provided with the clear understanding that the encampment is temporary, that they will be moved, and that residents who want to stay in them will be moved with them when the time comes.
Secondly, travel trailers parked permanently, very close together (6-8 on an average city lot), plumbed and wired, as a sub-300 square foot style of living. A good way to do this would be to buy several hundred Airstream 28-footers, but without any of the gear necessary for actually traveling or living on the road. As this is single story, and thus low-density, some planning would be required to choose the locations, but a great deal of flexibility would be had by not treating them as single-family homes. For some low-income people, and some homeless people, this would be all they ever want in the way of housing.
It would, in any case, be a lot more than they are getting now.