I'm not sure where you'd be able to find a "private" office in SF which is cheaper than a studio and where people aren't going to notice that you are living there. The cheap offices are usually larger office spaces split up. I.e. close quarters. It's the neighbors you need to worry about, not the landlord.

Keep in mind that a net connection is also more expensive at an office, you'll need a gym membership in order to take a shower, eat out every meal, regular chiropractor visits, psychotherapy sessions, etc. If you add it all up you probably won't be saving any money.

1) If you at the point of considering living in your office, then you are past the point of worrying about social acceptability. Don't pay attention to what we say, it sounds like you need to figure out if you will get away with it in your particular situation, and then just do it.

2) I think if you are finding studios as expensive as private offices you need to broaden your search area a bit. Generally it is cheaper, easier, and more socially acceptable to use living quarters as an office rather than the other way around.

3) You are that your business idea requires you be in that expensive area ? Maybe you could make a slight modification, and move to some foreclosure stricken area where you can rent a whole house more cheaply, and arrange with San Francisco friends to stay with them a few days a month to get done whatever you need to get done there ?

4) I regard posts like this as signs of The Coming Economic Collapse. ;)

what differentiates it in the eyes of the law are zoning and housing standards.

I know at least one warehouse in Hoboken demands to see your apartment lease before they let you rent a room.

Incidentally, "living" differs from "accidentally falling asleep" if you also keep your clothes and personal items in the office. And if you don't rent an apartment elsewhere.

That's one reason to sublease.