In all honesty, people who are 18-23 cannot enter into a serious relationship. Unless of course they are well to do financially. I'm not even thinking (well okay I'm thinking, but only thinking not doing) about dating until I get a college degree.
That's kind of a nonsensical thing to say, man! I was 23 just last year, had a college degree, my own place, and had a job that most people make a career out of! There are guys I know who are 22 who are in the same set up. None of us are "well to do financially" but all are ready for serious relationships, and over half are already happily married.
Also, a lot of guys don't go the college route. They may enlist in the Army, or pick up a trade. If that's the case, a lot of them are set in their careers by 18 or 19, and totally ready for a serious relationship.
I think it really just depends on the person, not on any certain age or education status.
- Topher