I went to college when I was 18. My first summer, I returned home and got a job. After that, though, I stayed in the college town during the summer and worked there. My parents were fine with it, and still helped me out some (and paid for my college). We had a good relationship, but my mom and I clashed enough (two strong, stubborn personalities) that it was best for all of us for me to get out on my own since once I turned 18 I wasn’t about to let Mom dictate my life anymore. I never looked back. My parents and I maintained a good relationship until they died.
Headed off to San Diego for Navy boot camp a week after I graduated from high school. 4 years later moved back in with my mother and stayed there off and on over the next 4 years. Finally got a place of my own and lived there for the next 26 years.
I had just graduated high school. I Got in a fight with my Mom over cleaning a bathroom the very next day. Decided to move out, left with my music library and gym bag of clothes. She said I’d be back in a week, took much longer and I didn’t move back in for the reasons she predicted.
Graduated college at 22, back in '85, and moved in with my girlfriend, though in the same city as my parents. Never moved back, married her a couple of years later. (also: I still can’t believe the sanctimonious Dallas Morning News ran the Times Herald out of business)
I was living with my parents in my hometown in Maryland all through college. After that, I got a nice fellowship to grad school in California. I got a car and went there. That was it. It was sad, of course, but my family has never been particularly sentimental, and it was always understood that we kids should and would fly the coop at the earliest respectable opportunity. And so I did.
Moved back home at the end of the summer after college graduation; spent a few months combining part-time jobs, part-time volunteering and job hunting; landed a job and moved out of state.
Many of my classmates had lined up their jobs or grad school plans before graduating, but I figured hell nah, one thing at a time. Since I was fortunate enough to have a welcoming family home to go back to, I went there.
Moving into an apartment OF MY VERY OWN was pretty wowza, though. Slightly marred by the fact that the fridge didn’t work and I kept my perishables out in the ambient-temperature stairwell, where the New England December climate did a fine job of keeping them cold, till I could get it replaced. 
When I was in college I think I considered myself still living at home, but when I went to grad school I no longer did. I didn’t even think about coming home for summers, since I was working. And pretty soon my parents sold the house.
Kept my parents address as my place of residence while I was away at college, even though my dad informed me that I was considered half resident / half guest. Two months after I graduated college, I got married, and reached permanent guest status at my parents house.
As I have never lived nearby, I have spent many nights at the house since then, most of them in a room other than my original bedroom.
At 18, I was home from college for spring break, and my father was making life hell for me, as usual. I hopped on a Greyhound, went back to college to pick up a few things, then went to NYC. I arrived there with $17 in my pocket and got a room at the “Y”. Got a $2.50/hr. job and scraped by until something better came along. Eventually returned to finish college, before returning to NYC for the following 25 years.
I lived at home until I was 20. I was working at a gas station and making my way through my pilot licence. The day I passed my commercial pilot licence flight test I was invited to interview for a flying job in a different town. I did the interview, got the job, and moved out the next day. I wasn’t ready for living in the big wide world, too immature, but I sorted myself out eventually without doing any more than exasperating my flatmates.
Did both college & grad school not living in my parents’ house at any point, but still storing some crap there and still receiving some official mail there. e.g. their address was on my driver’s license. And, at least at first, receiving some cash assistance from parents.
I’d done ROTC during college and once college and my waiting period ended I was called to active duty. At that point I moved out of state onto a USAF base. It was a couple years later that I changed all my mailing addresses and got a new driver’s license. I think I was about 28 when my dad remarried and wanted to update/upgrade the house and wanted all the kids’ crap out. At which point I stopped by, looked at it all, and simply pitched it. It had become both useless and meaningless to me in the intervening decade.
So somewhere between age barely 17 and age 28, depending on which event you consider to be the watershed.
For damn sure when I left for my first week as a freshman in college I had no intent or expectation of ever living w my parents again. Not that we had a hostile or defective relationship; I was just done with that phase and ready (I thought) for the next phase.
When I graduated high school, my parents informed me that when I turned 18 in less than a month, I would have to find a new place to live.
Spent a couple months couch surfing between some friend’s houses who still lived with their parents, didn’t tell them (the parents) I was homeless, just spending the night. Some nights I spent in my car. I never thought of myself as homeless even though that’s what I was.
Found a cheap apartment in a sketchy part of town. Moved on with my life from there.
My parents would sometimes ask me why I didn’t visit them more often. 
As an aside, I’ve seen several posters use the phrase, “live at home” to mean living with one’s parents. It’s pretty standard, but I always found it a bit amusing. In my 20’s, people would sometimes as me if I lived at home, and I would answer, “Where else would I live?”
In college, I lived in the dorms, but still came home for summers, and much of my income was still from Mom. Though for the last summer or two, I stayed most of the summer doing research.
For grad school, though, I moved across the country, with my own apartment, and lived there more or less year-round (a few trips home, but not more than a week or two at a time), and completely financially independent.
After grad school, when I moved back to my old hometown, I did stay with Mom for a little less than a month while I found a new apartment: Apartment-hunting is a lot easier when you’re already in the area. But it was known right from the start that that was a strictly temporary situation (for one thing, I moved most of my stuff in a moving pod, and I didn’t want to pay more than one month’s rent on it). That said…
I still have some things delivered to Mom’s address, just because there’s no good way to get packages delivered to my apartment. My grad-school apartment, each building had a few large mailboxes out front, and when you got a package, the postman put it in a large box and left the key in your personal small mailbox, but my current apartment doesn’t have anything like that. Though nowadays a lot of drugstores and the like do Amazon pickups, so I’m becoming less reliant on that now.
Thrown out at 18
In 1989 I was living with my mom and brother near Baltimore, and that fall I went to college near Philly. The first time I came home on a break, I could tell that it wasn’t actually “home” anymore: Mom and bro had quickly established their own routine, and I no longer really fit in (if I ever had; they were always alike, while I take after Dad). But I couldn’t do anything about it while I was in school, and since I spent most of my time in the dorms it wasn’t too bad; in the summers I worked, and partied with my friends.
I graduated in August 1993 (a month before I turned 22), but couldn’t afford to move out until April 1994 when my best friend told me there was a room available in the house she shared with some people. I moved in, and never went back to my mom’s house. The shared house situation was cheap and had some benefits, and I made some life-long friends, but I soon realized that it wasn’t really for me: six months later, I moved into my first apartment. I’ve lived alone ever since, except for 2008-2009 (ex-boyfriend).
Grad school.
23 yo I finally moved out.
I got a full time job right after HS that involved a 45 minute commute. My hours were 2nd shift, 3-11, 2-10, 6-12:30am. Or the dreaded split shift. I paid my Mom $50 a week room and board. We rarely saw each other and they’d often take off for 6 week long road trips as newly retired young 50 somethings. While they were gallivanting across the US Dad put me in charge of the house and making sure bills got mailed off in time and to keep an eye on my younger sister still in HS.
They’d return home long enough to service the van and plan the next trip. After I moved out my sister joined the Air Force and the folks sold the place.
A few months before I turned 19, my mother informed me and my 21-year-old brother that she was selling the house and we had to move out. So we did. About 2 years later, I joined the Air Force and moved across the country to California. Been here ever since. I’m 60.
Three months after I turned 16, my grandmother sent me to a boarding school to get me out of a bad home situation. My mailing address was then at the school, and I never again lived with my mother or got mail there. I went on to college, dropped out after a semester, got an apartment and worked for a year and a half (during which my mother sold her house and moved away), then a different college for two and a half years living in apartments and rented rooms, graduated and started work and bought a house trailer, then bought the house I’ve lived in now for 39 years. My only big regret is that I wish I could have left my mother’s house much earlier.
Moved back in from college dorm life (age 18-23) and worked full time while living at home. At 24, I remember me and a guy I worked with said that we weren’t going to be living at home at age 25. Started apartment hunting and found a little place for about $450/mth in 1998. Was dinky but perfect for a single guy. Got along fine with my mom and she helped me apartment hunt, it was just time to have my own place.