This is how you get housing tenements, and SF has a history of over-paying for impermanent housing solutions (like tents in a parking lot, or cots in a navigation center).

Not all buildings in SF are high-rise open-plans. If you're imagining converting Salesforce tower, I see how that would seem impractical.

Most commercial office space in SOMA (old warehouse buildings) can be converted into live/work lofts.