That's complicated. The first time I moved out of my dad's house was when I was 17, but that was to live with my grandparents. A few months later, at 18, I moved out of my grandparents' place to live with a friend's family. About 6 months later, I moved back in with my dad. When I was 20, I moved out of my dad's place again, to live with another friend's family, and after about a year, I moved in with my other set of grandparents. Now, in a few days I'm going to be moving to the same city as my dad, renting a room in a trailer with an older disabled man, and the owner of the place. I've spent approximately a year and a half living away from family.
So really, not counting when I moved out of my mother's place at 15 to live with my dad, the first time I moved away from my parents was when I was only 17. The first time I moved away from living with members of my own family was when I was 18. I've never really had a place of my own before, and the friend's families I lived with pretty much treated me as another member of the family, so the arrangement I'm going into will be the closest I've ever come.