How old must I be before I can move out ?

I have a question that no one can give me a straight answer to. If anyone can help me it would be exteremly appreciated. I wanna know what the minimum (lowest) age is for a teenager to move out of their parents house without getting in legal trouble. And can a 17 year old move in with a 21 year old in a relationship ?

An unemancipated minor can normally move out of the home without problems when the minor turns 18. Whether the police will always make a seventeen-year-old return home, particularly if that 17-year-old is living in a safe and appropriate environment, is a question of policy and not of law.