Do the $800 friend bike for $750 and a beer and spend the other $250 on accessories like padded shorts, shoes, bottles, underseat bag with tubes, tools, etc. It'll get spendy quickly.

That CAAD10 is a great bike and basically the same components as the 2014 one. At 2015, the introduce the new 105 components, so you're just looking at a slightly older bike. If the friend is being honest and it's not got more miles than he's saying, you're saving a couple hundred for living with a few minor paint knicks and the other stuff that has, no-doubt, happened to the bike sitting around for the last few years.