I moved out just before I was 23.
As soon as I was working I paid my mum some rent. Not the full market rate, but something.
My parents encouraged me to stand on my own feet and take responsibility for my decisions when I was quite young. They would always give support and advice (even if I didn't take it). I don't think they had to bail me out of any serious screw ups.
I'd hope my kids could do similar and felt that I was there to help out if needed. This may be hard for my older son who has Asperger's Syndrome. My goal with him may take longer to achieve, but I just want him to live and indepent life.