Garage sale bonuses
You find 'em. They are rare, but there are some out there. You have to sift a LOT of spoil to find the nuggets. Same is true in gun shows. Ditto flea markets.
Know yr prices, shop around, be prepared to dicker, be prepared to walk away if the price won't negotiate to something reasonable. Bring cash--offering spot cash instead of a check or something is sometimes a clincher. Above all do not go with a shopping list--you'll be disappointed at what you failed to get, and blinded to other possibilities.
Occasionally you find a screamin' deal offered by someone who doesn't know its value. Occasionally you find exactly what you want, and can negotiate a fair price.
If you don't mind putting in the time, that is. But the same thing could be said about estate auctions, farm auctions, or any other source of deals for the average person. Once it gets into the hands of a knowledgeable dealer, forget it--HE has to cover the cost of the item, pay his expenses, and make a profit to boot.
Look at it as a day spent outdoors, walking around. Take yr wife; she will enjoy looking over the antiques while you look for firearm stuff.
As to legal: As I understand it, FTF sales between residents of the same state are perfectly legal within that state, no FFL or any other documentation required. For my own safety I have the seller sign a receipt for the cash in exchange for the firearm, so I can document later that I bought it legally and in good faith, although the question has never come up after the sale. I offer the seller a similar copy, a receipt from me for the firearm, and they usually take it.