1.) craigslist.com is pretty sweet. Just a thought.

2.) A road bike would work fine. I've got a touring rig because I'm heavy (220lbs) and I like to carry a whole lot of gear (and sometimes my girlfriend).

3.) It will need to have braze ons on the rear so you can have a rack. Any touring set up will have them, but make sure the road bike you are looking at has them. They look like an extra threaded hole. Check out planetbike.com for their fenders and see what you need to mount them. Those fenders rock and they seem to be aplicable to any bike.

4.) My bike has clipless pedals which I have shoes for. Also though there are plastic inserts that my bike came with that go in one side of the clipless pedal so you can ride with regular shoes. They can't be very expensive and it lets you have a more usefull bike for whatever you want to do.

Oh, and ask your parents if you could decide on a value for a car and whatever you get below that you can have the rest of the money for a bike because it seems like the healthy and fun thing to do. I've found treating buisiness like that logically with my parents to work pretty well (but not everyone's parents are that cool with stuff like that). Good luck.