Full-time in the San Francisco Bay area while working?

I agree with others that your best bet is finding a park as far East of SF as you are willing to commute. The further East you go the less expensive it will be. The BART is the way to go; you can drive to a station and then take the train in. You also might consider renting an apartment in these areas rather than purchasing an older RV which you will be responsible for any repairs etc. Many people commute from Tracy, Walnut Creek, Vallejo, Pleasanton where rents are more reasonable.