+1 that for that price you can find a decent used bike.
However, in order to have any hope of enjoying your bike, it MUST fit. Take some time to take some measurements and get an idea of what to look for. It is a dance, and there are no absolutes. This is probably the biggest risk in buying a bike sight unseen.

Bike style: Do you intend to race? Is the bike for short recreational rides, or casual road rides? Do you have any physical issues (neck, back) that might limit the type of bike you are seeking?

Here are a couple pretty reliable online bike fitting tools - you'll see that there is some variability in the recommended setup, but they will give you a general sense for what size bike will fit, and what geometry might suit your needs.

http://www.competitivecyclist.com/za...LCULATOR_INTRO
http://zinncycles.com/Zinn/index.php/archives/2141