Hi,
3 years ago, I entered this pagent. You don't enter the pageant, you apply, kind of like a job so they can breifly get to know you in writen question form along with a picture of you. Then they call for a phone interview if they are considering you for the state pageant. If you are chosen as a finalist, most of the money needed is from sponsors. I was in Miss Illinois Teen USA and I don't know if its the same in each state but I needed at least $1,000 in sponsors. Then you need to purchase an evening gown, one piece swim-suit, and and interview suit. Food is included in your stay at the hotel (with a room-mate) They set all of that up for you. You can pay extra to have their stylists do your hair and make-up or you could do your own. Then tickets for family and friends to come see the pageant I remember are very expensive but I don't recall how much.
However, despite all the expenses, it is totally worth the experience. Its a big oppurtunity, PLUS all the FREE stuff from their sponsors such as make-up, lotions, even scholarships!