I need some schooling on road bicycles. My buddy has a decent (to me) bike around $1300 and wants me to ride with him. I know he goes on 50mile rides quite often and I figured it would be fun and a nice way to drop a few pounds.

Now My budget isnt that great ($500ish, more if I save) and am wondering what is decent. I have been looking on Craigslist and this 2007 GT GTR Series Three is standing out to me if it fits. http://fresno.craigslist.org/bik/974818104.html

What about building my own bike? I could figure it out pretty easily as Im pretty mechanically inclined and had a mountain bike that I was constantly messing with but it got stolen on campus. This bike wont be rode to campus or other errands and will only be used for actual bike rides.