In my culture there's nothing weird about living with your parents into adulthood. *shrugs* Or at least until marriage. It seems like it's really only American culture that views people as emotionally stunted if they don't fly the coop the second they turn 18.
I'm not emotionally or financially dependent on my mom; I half-own the house we share, pay my share of the mortgage, utilities, and the equity line from which I borrowed to take care of bills while I was out of work (which is actually the majority share, as my income is now significantly higher than hers). I buy my own groceries and do my own laundry. My mom and I maintain separate lives, much like roommates, although we do hang out and have mother/daughter time and do things together like have lunch and go shopping. We haven't done that in a while because my grandmother's illness has been a big preoccupation and has taken over some of her life, and a significant though not as large a portion of mine.
I live pretty quietly - I had my wild years in college where I partied and drank and did pretty much what I wanted to do because I was 400 miles away from home and on the loose, so I got that out of my system (and still managed to graduate on time and with a reasonably good GPA). My mom fully recognizes that I am an adult and doesn't place any ridiculous rules or restrictions on me. I am expected to help keep common areas neat and clean, which is a reasonable expectation, and pay my share of the bills, but she doesn't place any restrictions on me like where I can take my car (that I bought and paid for and pay insurance/maintenance on), where I can go and how long I can stay, who I can bring over, whether I can have someone of the opposite sex in my room with the door closed, etc.
The one thing she was rather inflexible on when both my brother and I were living at home was no overnight guests of the opposite sex, but she's softened her stance on that one now that I'm the only one home - mostly because she knows I'm sensible and I'm not going to bring home a different guy every night of the week or anything. I didn't violate that rule when it was in place, and now that it's not in place, I'm not taking advantage of it, so I think she realizes what she can expect from me.
I do have a (reasonable, I would think) expectation to my privacy and my mom respects that and gives me what privacy I need. Just because I live with her (or she lives with me

) doesn't mean I'm an overdependent baby who can't bear to be away from my mom. It's just a better deal for me financially to live here. I put money into this house rather than throwing it away on rent, my mom treats me like the adult I am, we get along fine (for the most part), and she understands that I don't need her watchful eye on me 24/7.