Public housing costs more than $400,000 per unit to build [0], assuming you can find a site that the neighbors won't kill.

Increase the city income tax from 1.5% to 15%. You'd need around 9 $300k households, each contributing $45k, to build low-rent housing for one family.

[0] https://sf.curbed.com/2018/5/22/17380702/farrell-affordable-...