Can you move in with your best friend and her parents if they said it was fine if you helped pay for stuff?

If you are a minor you cannot move from your parent's home without their permission. Even with permission, your parent(s) would need to give a written, notarized statement to the adult(s) who are allowing you to reside with them. The statement has to give the date you were moving in and the length of time you were staying; permission for medical care, school issues such as enrollment, and the amount of money agreed upon for your support and how payment is to be made. Such situations are generally referred to as temporary, voluntary custodial transfers, the law defines "temporary" as three months or less.