Call the LEO and ask.
But are you prepared to go through the hoops if 1 firearm you get was stolen (receiving stolen property)?
The normal attitude is "We want to remove these from the street.", and you can expect to get some unwanted attention if you setup at a "buy-back" program.
Just put an ad in the local newspaper, get seller's info, and report suspicious purchases (like a rifle that could go for $700, but the seller is willing to accept $100).
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)