Your "friend" is not offering you a great deal. I'd only give it a passing thought if I was actually lusting after that exact model in a 2014 or leftover 2013 model and your friend's bike was cheaper. Even then, once you account for used bike/no warranty, mileage your friend accumulated, maintenance he did not do, wear items he did not replace, and any gratis service on a new bike you'd get if you bought new, it's a rather poor deal.

But don't haggle with a friend you want to keep, merely casually pass on the deal.