Do you have a loan approval for $400,000, or have that amount to put as a down payment? Either way, $400,000 is a lot of money, so congratulations on saving the amount that you did! San Francisco is a very competitive market, and also very expensive. However, there are definitely studio's, some 1 bedrooms, and even some fixer-upper single family homes out there in your price range. It all depends on the locations and what exactly your needs are in a new home.
I'd love to hear a little more about you and what exactly you're looking for in a next home, and I would be happy to send any potential options your way! I also have a MLS search engine I would be more than happy to give you access to so you can do some searching on your own if you prefer. Either way, please let me know if I can be of service in any way, and I would be more than happy to help! Hope you had a wonderful holiday season thus far, and I look forward to hearing from you.
All the best and good luck with your search!
Realtor, Vanguard Properties