I will award best answer. And by the way, this doesn't include a case where maybe you are going through financial difficulty and need to move with your parents for a temporary period of time. I mean when should you start looking for your own place (or room mates)?
Be out of your parents' home within a year after you finish grad school. You get a year to live with the excuse "I just graduated, am looking for my first place and am struggling with my educational loans." Then people expect you to either have your own place or have a bunch of crazy roommate stories...
C. People have adopted a second adolescence in the latest generation (Y?), combined with the down economy eliminating post-graduation jobs. If you work part-time hourly retail, you can't afford rent and food. Not to forget the number of graduates returning to school for a more useful degree. How can you pay for rent and classes? Not easy.
I think it depends on the person & their situation. If you are a college student, I think it's fine to live with your parents while going to school. If you are a 30 year old with a kid & significant other, you should probably find a place of your own.
I think if you live with your parents until you finish school is perfectly fine and maybe a couple years after so you can get settled in job and can finance such a move. Any older and I believe its too old.
I actually agree with your update. What is difference between splitting the bills with your parents vs. a friend or roommate? As long as you're contributing, you're more like a roommate, than the kid who still lives with mom & dad.
I don't think there is a specific age just as long as you are not bringing your wife to the home you're good.
If you ask my parents, they'd tell you, right after you graduation HS. Age was not a factor, you either got a job or went to college, and you lived there, not at home. You could visit, but you never lived there again. That made us more independent & mature. I think after college or if you don't go, get a job & get your own place within a year. But you pay rent, a small amount, but you're an adult with a job, so you pay. And if I were the parents, I'd save it for my kid & give it back for their first & last month's rent when they move out. So, early 20s. BTW, I left at 17, went to college & never lived at home again.
I don't think its an age, but a point in your life.
If you graduate high school or get your GED at age 18, then don't do any other schooling, then maybe for you 20-22 is a bit old to still be relying on mom and dad.
But then, if you go to college, and get out 22-23, then it would be totally fine to stay a year or two to get your life in order before heading out.
What if your parents own a farm, or some other business that requires you to live close by (horse-care, hotel, etc) then maybe living there for several years getting to know the business would be totally fine! What if your parent is sick and needs help? What if you are sick and need help? (Long term illnesses or loss of limb or something)
The point is, its a grey area. Its sad we look down on people who live with their parents, because we don't know their story. If we were to look down on someone, it should be someone who is refusing to grow up, and refusing to become responsible for their life.