Thank you all for your thoughts, and thanks especially to Tetsuya Hondo for the helpful reminder that sellers would probably get less when going to a dealer. I'll just try offering the kbb price and hopefully get something decent for $5000 or less.
@neogodless, I also looked out for VW Golfs but the offers are rare.
Regarding Zipcar: My husband looked into it and hopefully managed to get an account on a discount from his company. It's not so easy for foreigners who just got their CA driver's license to be accepted by car sharing companies. We tried getaround, too, and they wouldn't accept us unless we provide a letter from the DMV at home that we have held our licenses for XY years. That will take some weeks to get, I think. I don't have my CA license yet, practical test is in February. We will use Zipcar as soon as the membership card is here to get around until we have our own car. Like I mentioned before, we did car sharing at home and my husband said that he wants hassle-free driving with a kid, no carrying a baby seat around town, no fear of food stains or vomiting in a shared car etc.
So we decided that owning a car is our permitted luxury while we're here. It is a special time for us and we want to get the most fun and awesome experiences out of it. Having a car in your garage (for which we have to pay no matter what, and no, we are not allowed to sublet the space...) and being independent in that respect, helps with that goal. Which actually beats the financial goals for the moment. I'd rather have an unforgettable experience living in another country for a few years and have my retirement postponed for a few months... My husband does work he loves anyway and I do not have a work permit here (yet), so for now I have the luxury of figuring out what to do with my time as if I am already retired. :)
Again, thanks for your comments and all the best.