You will need a parent/guardian to help sign a "Modeling Release" with the photographer to protect your rights and the rights of the photographer. Be sure to never shoot alone so as to protect yourself (and the photographer). From that point be ready to do unpaid, minor paid or you paying a photographer for modeling work.

As you are just starting, you will need a professional starting portfolio before you may get any paid work, however, the stipulations are based upon what a photographer needs or wants. (ie: photographer needs a specific ethnicity, height; updated portfolio; may want to do an photograph different from his normal work).

Hope this helps.