This kind of happened in the UK already. For instance, Bournmouth, a town on the South Coast, attracted homeless people for the obvious reason that the climate is typically warmer than most other places. I assume SF held a similar initial attraction?

In response to this small influx, local authorities encouraged charities to set up shop offering help to these people with drink/drug/social problems with a view to getting them back into regular housing.

Some years later, the problems have become much worse although the number of charities operating in the area has grown exponentially.

Speaking as someone who has experienced homelessness, for a short while, I believe the only practical solution is to give people housing at the outset before the desire/need to move elsewhere takes root.

The obvious response is that it is not that easy and would be unaffordable but my retort is that the current situation is likely costing a lot more while, at the same time, not fixing anything - other than creating multiple charity jobs.