Believe it or not I have actually organized cage fights for a facility. Although I am not a promoter I do know that all fighters must be approved/validated through it's state overseeing body, which in most states is the state boxing commission.
Call you state's boxing commission and find out what you need to do. They usually check your address, birthdate, phone number, height and weight. As for money involved, it's usually minimal (less than $50).