Alot of students own here at Penn, but one thing is (almost) constant among those who do... PARENT MONEY! There are alot of good investments if your parents are willing to chip in. You have to consider that when you're deciding if you want to buy. I saw lots of students who owned places when I interviewed and so I thought it would be a good idea for myself. But, I didn't realize that many of the students were still getting money from their parents. At some places living far from the school might be an option depending how you feel about commuting, though you have to really investigate the parking situation beforehand. Med students are often the last to be considered for parking, even at suburban/rural schools.
The one exception I know of to the parent money rule is a girl who bought an old beater in pretty far West Philly. I really wanted to stay either close to the school or in Center City, and both of those options are too expensive for a stipend. As for Andrew Doan, he signed up for the military and that supplements his residency salary. Figure you won't be making much more as a resident, so if you buy then the prospects aren't much better unless your spouse is bringing in good money. On the other hand, residents usually don't have a problem getting parking, so here at Penn most of them (like most of the faculty) drive in from the burbs where they can buy more affordably.