Didn't expect this to get so many replies. I appreciate them all as I soul-search about options. A little more information might be in order.
About the living at home bit - it's a mutually agreed-upon situation. In three months my younger sister will be away to college so it'll be just me and the parents. I have all the freedom I really want or need at the moment, and while I do plan to move out eventually, my situation is such that I don't have much pressure to. I do pay "rent", so I'm not just taking freebies, but that's somewhat immaterial and a private arrangement that's between the family.
A few things that I've noticed in the replies that have been unexpected - there are more folks paying bank notes to fly than I thought. It may be a stupid decision, and I appreciate everyone who has pointed that out, but that's why I probed for the information from people who've done it.
Partnership would be my natural first inclination, but I don't have too many pilot friends with the financial ability to back it. Those who do are looking for Bonanzas and the like, so I'm priced out of the group there. I'm really just looking for something simple, fixed-gear, and (relatively) cheap.
As far as aircraft choice, a few have pointed out the 150/152. At 6'3 and just a hair over 250#, I'd basically be limiting my trips to short hops with a pax or solos. The rationale behind something like a 172 is that I can bring a friend and a couple bags and still be relatively comfortable doing it. I rent a 150 every so often but I couldn't see myself owning one.
Here's another thing I'm pondering - an RV. I don't have the time or patience to build yet (although my later-life goals include doing it), but there seem to be several decent candidates for sale in the pre-built/pre-owned category. I do like the relative performance gain from an RV - beats a 172 easily.
Oh, if only this decision was easier...