Don't sell to a fellow mechanic!
As a someone who's never bought a bike new and fixes up bikes for myself or friends, I don't know if I could ever buy from a flipper.
I'm sure they do quality work but I see their ads and just think, thats not hard and I could do that myself. In my market in the Twin Cities lots of people are riding vintage frames. Mostly old raleighs, Schwinns a fair number of Japanese bikes and Treks as well. flippers usually charge around 200 for a basic scheinn and closer to 300 or 400 for a nice trek. Personally I think those prices are steep for a recable, new chain, bar tape, and brake adjustment job.
The price reflects a convenience factor. Most people don't know how or don't want to fix up a bike, so they are willing to pay extra for a cool vintage bike thats completed. Me id rather save for another frame and do the work myself.