Most of my better deals on beaters and donors have been from friends/family, forums or discussion groups, or local auctions.
My 'network', so to speak, has done a lot more for me than wandering around and checking every gun shop and pawn shop.
I have tried the old "what have you got in the back" approach. Diddly, there, except for a really cheap AR barrel.
I'll work with some really ratty, broken, rotten, Bubba'd guns. But the stuff "in the back" was all so far gone that it wasn't even good for parts.