I know you said he's not too interested in mortgages (who is at that age?), but there are strong incentives to take one on early, or at least save for a deposit. It's one of those things where once you take one on, you think "damn, just wish I'd have done this earlier!"
Couldn't agree more, I'm 28



An extreme example, but mortgages go down over time, whereas rent always goes up.