If you need to be in SF past midnight you need to either live in SF or have a car. Its a sad and pitiful fact about our public transit reality. There is a late night AC transit (Bus) transbay option, but it runs very infrequently and is sketchy in terms of where you have to catch it and where you will end up. It can be pretty amusing though. My friend calls it the "Drunk Bus" that is about right..

Cabbing back to Oakland will quickly eat up any rent savings you would have living in Oakland. I have this same dilemma as a working musician, but I need a car usually to tote my upright bass and/or amp around so I'm screwed anyway.

Cabs in the city are not so bad cost-wise. If you live in the city (most parts anyway) you will hate having a car b/c you will spend 45 minutes parking and/or have to wake up to move your car before street sweeping/meters kick in all the time.

Good luck and welcome to the Bay Area.

The good thing about driving across the bridge at 3 am is that the traffic isn't bad then. Going to the city between 5:00pm and 7pm is pretty time consuming, though. You can save money living in the east bay, but you won't save much without living in a neighborhood of questionable character. Most people opt to save money by living with roommates in the city (SF), especially by living with someone who has had rent-control for years.