You get a sellers permit from the state board of equalization, here's the forms you need to fill out they can give it to you on the spot after reviewing your info. Just take it to the office that's closest to you. Find it on google. I don't think you even need a business license to get one because my step dad never got one but still buys cds at wholesale. I personally think it's the wrong time to get into a business like that right now unless you are buying shit hella cheap.
A couple years ago my boy and I started selling ecko shirts for $15 a pop at a flea market, we were getting them for $8 at the time which was real good. We were doing real good till some allah akbar mother fuckers came in with alot more money and had alot more stuff than us. So we slowly kinda stopped selling clothes. Another thing we did was buy jackets and jeans at ross and mark them up $10-20......
http://www.boe.ca.gov/pdf/boe400spa.pdf