AS Kekito said, you will need those 3 things.
You also should think about "return policies," i.e. you get up to 7 days to receive a full refund. You need to keep in mind the consumer protection laws of California, I don't know what they are off hand, but I know they're one of the more consumer friendly states.
You also should make sure that you're keeping enough for taxes to California, and anywhere else you happen to have a physical presence. If you're servers are located in a Data Center in, say, Texas, research their tax laws (even contact their Secretary of State) to see if you need to file as a company there and pay taxes. Some states treat having servers in a DC in their state as having a physical presence and will require you to collect Sales Tax from people in their.