several points regarding housing around wash u, in particular.
i grew up in the central west end (CWE), and just spent a few weekends learning the ins and outs of all the streets and neighborhoods while looking for a condo near the school.
if forest park is a big rectangle, with the med school on the east side and the ugrad on the west (about two miles across), here are the neighborhoods:
dogtown - south of the park. lots of young families. cheaper rent, but not as trendy a neighborhood, and a bit of a haul to the school (not on the shuttle)
u. city - north of the western half. similar to dogtown, maybe a bit more expensive, on the shuttle. typical place = 3br single family or 6 unit condo. keep in mind that if you plan to drive to school, you'll be spending $400 or so on the parking permit.
CWE - east and northeast. a huge mix. near the medschool are lots of condos, in low and high rise buildings. north and northeast of the park generally consists of enormous, old mansions - 3 story, 10 bedroom affairs with elevators and carriage houses that could house several students quite happily. this area also has some streets with smaller houses, as you head towards u. city. further east (starting at boyle), things do get pretty sketchy in patches. we're talking boarded up houses, or real estate-wise, houses on for $40,000. the whole area is on an upswing (condos that were $80-$90,000 in 1999 are regularly selling for $200,000). so maybe buying in a patchy area will net you some serious gains.
forest park southeast: just south of the med campus. the latest really down and out area to catch the eye of a few adventurous souls. i tend to feel pretty laid back and safe, perhaps even when i shouldn't, and as a woman i absolutely would NOT walk alone at night, and i'd be cautious during the day. again, some real deals to be found, and potential for great growth, but not ideal if you're in the library until midnight.
tower grove/ shaw neighborhood: like dogtown, but surrounding forest park southeast, and extending southeast beyond that, around the botanical garden.
i settled on a condo a half mile or so from the school (industrial buildings means it's hard to get much closer without being in olin. even though places advertise "steps to wash u med," mapquest it to the school (660 s. euclid, 63110) because you may be in for a surprise. i decided it was worth the higher price, because i wanted an easy walk and nicer, safe neighborhood for the next few years. i'm also a couple blocks from the restaurants and bars of the CWE (north of the campus), so it's easy to get to the fun part of the CWE. plus, i figure i'll probably get it back when i sell, and if fortune is smiling upon me, the place might even appreciate a bit as well. i'll likely be trying to find another first year to share it with me, since it's 2br and 2ba. it'll probably be in the range of $550-$600, which is maybe on the higher side, but that's about half of what it will cost me to own, and it's worth that much to me to be in such a prime place, with a nice condo (large rooms and plenty of space, exposed brick, etc.), the place will be fully furnished and equipped with a washer/dryer in the unit, somewhat decent furniture (i'm ditching the freebie furniture i've in college and my current apartment), and come with free parking. ugh - run on sentence.
the school does send out info in june to help everyone figure stuff out. apparently, 90% of first years live in the central west end, generally in high rise places (because those are the easiest to come by). i've heard 8% or so live north of the park, and 2% live elsewhere.
i should add that much of this info comes from what i have seen directly or current students i e-mailed when trying to hammer out the details of what would be the best fit for me.
sorry to ramble on so long - this just happens to be stuff i've been quite focused on for the last couple months.
feel free to pm me with questions, and i can do my best to answer them.