https://www.usacycling.org/
Go there and read up on it.
There is a university racing program, and the USCF racing program, they are each a bit different.
The university would depend on your school, the USCF, you start at 5, and work your way up. Because you have raced before, you may be able to get an exemption and get moved up in class, but usually you move up through the ranks.
For clubs, it depends who you hook up with. Some have really good deals with local shops, some have deals with vendors directly, it all depends. I worked at some shops, and was able to get really killer sponsorship deals (helmets, bikes/frames, clothing, and other little stuff) because I knew all the reps, but that was years ago. Right now I am unattached, but as I said in my earlier post, I am in no shape to really race hard yet, so that is okay.