I go into the Gun Library when I need a good laugh. I hit the sales rack outside it looking for good buys. Problem is that no one can know everything and to buy long guns, pistols, surplus and C&R stuff is beyond anyone's abilities. I do OK buying Shotguns, fair on rifles but loose my butt on handguns. They might do better buying estates where large number of guns might help them if they over pay for some of them.
I bought a Remington Model 12, Remington Special pump gun with a tang sight, in mint condition for 15% of its real value. Heck the sight was worth more than a hundred alone. Reason it was on the sales rack was I was told the ammo was no longer made. I asked for their lowest, final sale price with no right to return it and they cut it in half again. I bought it out of petty cash in my pocket. My Winchester Special ammo is the perfect substitution for the Remington Special ammo.
My son bought a Gallery Special .22 short, Remington pump gun for $200 off the sales rack. Not mint it was worth three or four times the asking price. They told him that no one shoot shorts much any more and you can not hunt with shorts.