Guys, read the craigslist ad- the bike is 150 bucks. if it's in good shape, that's about the right price for that bike, probably. I'm assuming you're riding on roads though, in which case you'll want to change the tires most likely, so factor in that expense. Also you'll need, no matter what bike you get, a frame pump, patch kit, spare tubes, and a good multi tool--or at least tire irons, if not the tool.

So with that bike, probably add a good 70 bucks to the cost to get yourself set up.

Of course, if you are willing to spend as much as 500, there are better options. You get what you pay for, of course. The Jamis Coda would be fairly fast--the Coda series are basically flat bar road bikes, and the series runs the gamut from 450 to 1750 dollars. Obviously for you and most people the basic coda would be more than enough.