A recent affordable building in SF cost over $1 million per unit. That's completely unsustainable.
And you want and need precisely that in a house with fluctuating occupants of which a high percentage will have some sort of mental health issue.
Cutting corners on boarding houses will lead to fire catastrophes.
Nobody denies this. The question is whether said fire catastrophes really claim more lives than homelessness and wintering on the street. (Obviously fire catastrophes are a bigger PR problem and get more media attention, but is that really the appropriate metric for human suffering?)
https://twitter.com/MarketUrbanism/status/160882533241258393...
The problem is not just zoning. A boarding house simply doesn't generate noticeable income compared to standard residential housing, and with exploding land prices it simply makes no sense financially to cater to poor people.