I fell in that hole once.
1999 bought a mechanic owned 1997 Kona King Kikapu frame. Mechanic caught me browsing in the store and offered up his frame. This shop being 3 hours drive from where I live, I dropped my old broken Kona Sex Two to return a week later to excitedly pick up my new bike. Brought it home, inspected bike, cracked seatstay. Furious, I started the 6 hour round trip to deal with it where I was pretty much kicked out of the shop by the owner. Was a "private deal" according to him.
Never dealt with that store ever again. Nor that mechanic. Buyer beware.