Used vs. new doesn't necessarily mean you will save money. I will offer this suggestion...look into a 2016 Giant Defy 5 with 2x8 Claris groupset for $620 new. Relaxed geometry, aluminum frame. I purchased a 2014 new and have put about 6,000 training miles on it riding through two Pacific NW winters so far. It also travels with me when I'm working away from home. 100% reliable (although I did just upgrade the drive train to 2x11 so I can swap my power meter between the Defy and my carbon bike) . I would say I got my money's worth.
Keith