I remember back in the late '80's we were laughing at a guy we were training with who paid $30,000 for an extra condo parking space in the down town area.
A studio apartment in a really old house that has been awkwardly converted into a multifamily property. You'll probably not have any parking except on the street, and you'll most likely need to walk around the back of the building, up a narrow set of stairs, to a 'cozy' apartment with the bathroom door in the cramped kitchen. Something really weird like that.
$500 is the average rent in St. Louis depending on the area. North, Mid, and South county will obtain you a nice one bedroom. This will not get you anywhere in West County or Clayton. You could also use Rent o meter if you want to find out the rent in a specific county or street.
$500 - a poor quality bachelor / efficiency unit in the City core. As you move out to the edges, it will get you a fair 1-bedroom. If you qualify for housing assistance, $500 (of your own) will get rounded up into a, possibly clean and repaired, 2-bedroom (maybe a 3-bedroom on the outskirts)
Near downtown you can rent an old apartment with 3 bedrooms, however on the outskirts of the city (20-25km away) you can rent a fairly luxurious condo with 4 bedrooms and security, fitness center etc.
I'm near Ft. Meade, Maryland and $500 can maybe get you a bedroom in someone's home. It would probably be a decent area at least.
For $700 each, we're renting out two bedrooms in our home and that doesn't include utilities. Past housemates have told us that our rent is a little higher than most other rooms, but they were willing to pay it because they really liked our house, location, and well...us! :-)
I'd say my neighborhood is pretty nice. I personally love all the old trees and the contemporary home styles.