My husband (29) and I (24) are living on our 32' sailboat. She is our second; we lived on our 27' Catalina for a while before (he a year, me a few months since I was away in college most of that time). We are the 2nd-youngest sailboat-live-aboards, and there are actually quite a few young sailors and liveaboards where we are here in Portland, ME. The only couple younger than us just moved onto their boat this fall, we helped them find their boat and they got a 27' Catalina (of course!). There are two other young couples with sailboats and two single guys, but no single ladies. There was one, but this year her beau moved aboard with her. Lucky man, her boat is beautiful!
As others have said, of course, there are plenty of older folks on both power and sail boats. And, we have been told that "our parent's boat is really nice," and "Don't worry, I won't tell your dad!" when we ran our Catalina aground a few years ago. We didn't purchase a house, instead used our limited funds to buy a boat and pay off school loans. Still working on the loans part!