I say that if you're old enough to move out - and stay afloat money-wise - then you are old enuf to leave home.
You might want to be careful and try to not burn any bridges - just in case you ever need to move back home.
When I was 21, I was beginning to do things - socialize and all. (I wasn't getting into trouble - just beginning to enjoy living.)
One night, I was out late at a friends' apartment - the fella lived across the street and down about 4 houses. Anyway, we stayed up late - talking. No booze, drugs or gals. Just two guys talking. (If I recall - he did most of the talking... about his girl problems, etc.)
Anyway, I got home late... probably after or around midnight. I let myself in, and went to bed. The next morning, my mom read me the riot act - telling me that I needed to not stay out late, etc. (I suppose that was her right - to do so.) I told her that nothing was going on, and where I was (I even walked home - it was so close.). Well, that wasn't good enough for her. She railed on and on. Finally I said, "Well, if I can't do those things living here, then I'll just move out." She said, "Fine!" I said, "Fine!", and she stormed out. This was on a Tuesday morning.
Well, I had already been thinking about it, and knew of a small cottage that I thought I might be able to rent, and so talked to the fella that could rent it to me. I got the first months' rent paid by Thursday, and started moving out on Friday morning.
My mom found out - and again went ballistic. She hadn't figured that I would leave that quickly.
I won't bore you with all of the details... her phone calls to the psychiatrist, etc.
Let's just say that after I left, I knew that I couldn't go back. Ever. There were a few thin times... when money was non-existent - but I made do, and made it - usually with my own resources - or the help of friends.
So - if you're thinking of leaving home - try to make it on pleasant terms - that way you can visit from time to time - and still remain good friends with your parents.
They won't like your leaving - but it is something that youngsters do eventually. Hopefully.
Good Luck.
Regards,
Jim TX