As stated above, the sizing can make or break your riding experience. A really ace bike that doesn't quite fit can in the best case lead to irritation and in the worst case injury. Definitely shop around and talk to sales people. Get tested on a fitting jig (at a highend shop) so you know your size exactly. Buying used, from ebay or local classified is not so dumb, once you know your size. You can get a lot of bike for a few hundred! If you are mechanically inclined and see the bike itself as an enjoyable part of the overall experience then you will generally lead a happier biking life. You really need to learn about maintainance and repair because a bike that rattles, squeaks and wobbles is going to end up not being used. A mistake that some people make in the beginning is getting a lower quality bike thinking that it is "good enough" and then realizing almost immediately that this or that would have been better. If your budget is limited as you said then get a used bike, preferably with a quality steel frame and mid to high range components, Shimano 600, 105, Utegra, or Campagnolo Victory, Athena, Chorus and then be prepared to spend some time and a little money restoring or replacing. Ebay is a goldmine for parts and not least information. When you have been inside your bike yourself you will know how to deal with the small problems that inevitably arise instead of being a slave to your local mechanic. If you start with a quality frame then upgrades in various components make more sense. A quality hand built steel frame can be repaired and straightened, gives a fantastic ride and is a thing of beauty. A used aluminum bike is a bit of a question mark since aluminum fatigues and cracks. Then there are tons of other considerations, too numerous to test your patience just now. The learning curve is a fun ride as well.