What location are you looking at and will you have a car?
The harsh reality of our three locations is that housing within walking distance is seriously overpriced. Westwood typically demands $3000/month for a two-bedroom apartment near campus. Irvine and Berkeley are not much cheaper. But if you have a car that problem is remedied. There is some public transportation, but it will likely involve having to transfer.
In the past people have used air B&Bs with varying success. Most have worked out well (students who do nothing but study make great tenants), but on occasion there has been an unscrupulous landlord who demanded extra payments once the student was already settled in. If you wish to PM me, I can send you an email address of the office manager at the location you are considering.