If you're going it alone, there are none. Well, you need a finger. It would be good to have some contacts in that case that might be able to help you get your work seen. But basically—if people like what you do, they'll pay you at least something to do it for them. If you work for a studio, publication, or other company, they may want you to have a photography degree. At the very least, you should have a very professionally prepared portfolio that showcases the range of your abilities. The shots you had taken at the Photo Booth at the San Diego Zoo where you custom-angled the camera behind the curtain in a fine self-portrait can be left out of this one. Yes, even though you were making a really funny face.