Seems roughly in line with UCSF's entry-level post-doc compensation: https://postdocs.ucsf.edu/pay-and-benefits
That too, of course, is too low to live comfortably on your own in SF.
"Comfortably" varies by person. I know many people living fine on less in San Francisco.
While single and working at a startup back in the dot-com days, I shared an apartment in the Richmond district with two other people. It didn't seem all that unusual. I assume people still do that?
Seems like it would be okay temporarily until you get a raise and the stock options kick in.