The UCSF website has info on housing, both university owned and private. The lottery for university housing happened in March, so if you are accepted and want to share a bedroom with another student (there are no singles first year unless you have a family), get on the waiting list. Otherwise, they run a community housing bulletin. Most people in SF find housing on their own, it can take a solid 2 months if your budget is small and want things like a kitchen. Try craigslist.org for listings, and if you are getting close to starting and haven't found a place yet, pony up the money for the private listing companies (60-100ish), they have more leads.