I don't have a spouse / savings / parental support, and I live a 7 minute walk from the hospital. It is a little studio... but I made it happen. Yeah, I feel a little poor right now, but I cover my expenses. I feel like I really can't complain, since I am single living in an awesome city (and I have the time to enjoy it), and I didn't expect to be making $$$ while in residency. There are two others that are closer walking distance than me (we are all in the Pacific Heights neighborhood), and I don't know the extent that parental support may play a roll. I know of two others in walking distance, they have spouses, I don't know their financial situation... as I go through the people in my head, I really don't truly know the financial situation of anyone, it just be a guess. CPMC is in Pacific Heights. If you look at a map, there are people living in the Tender Knob, Richmond (the neighborhood, not the city), Presidio, Laurel Heights, Sausalito, Berkeley, Oakland.
People can moonlight nearby. Alta Bates in Oakland, a place in San Leandro, I think once upon a time someone did SFGH, I hear there are two other places people have recently moonlighted at.