If there were a million empty houses in San Francisco that were available free of charge, there would still be a massive homelessness problem because the real issue is not lack of housing, it's drug addiction and mental illness.
Then there are the chronically homeless. Those with no desire to become productive. These are the people that imo would be helped by forced rehab programs. But make no mistake, many, many homeless are the first type, not the second.
Here's a study someone else posted: https://news.ycombinator.com/item?id=33010913
"The data shows that over 70% of all of SF's unhoused people became homeless while living in San Francisco"
According to a 2019 survey [0], only 70% of people were living in SF prior to being homeless, and of those 70%, approximately half had lived in SF for less than ten years.
To me, that's staggering if 30% of the homeless population was already homeless before they moved to SF, and if another 30% became homeless within 10 years of moving to SF.
[0] https://en.wikipedia.org/wiki/Homelessness_in_the_San_Franci...