When you have saved enough money.
I lived in my parents house and stacked up for 3 years rent free before leaving.
Probably the best decision of my life so far.
when I stayed with my folks for 7 months after graduating for undergrad...for the most part it wasn't bad and I was able to stack up dough but I did butt heads with my father about somethings plus I was used to going in and out as I pleased and having females over...things my folks weren't with..so when I got accepted into grad school for the spring semester I was out and haven't looked back..8 1/2 years