It would be lots more interesting to Parents if they said something like "May hold the key to maturity", where they learn how to stop a 17 year old from having the behavior of a baby. ;)
A school days friend of mine stopped developing at age ~17. Some very rare condition. Now he's about fourty and about to out-live his mother. However, there's no chance he'll ever live on his own.
Plenty of people live on their own at the age of 17.