Q) What price guidelines should I use to purchase a used firearm ?
A) As a general rule .... Firearms are like cars, by demand and collectibility.
Saying that from a seller's point of view they want the best price they can get. Firearm seller's often think what they pay for something relates to it's value, there is nothing further from the truth. Back to a used car versus a new car. You don't get new car prices for a used car unless it is very collectible or in demand. Also sentimental value means nothing to a buyer, so if you are attached to it keep it.
From a buyer's point of view always haggle on price even new firearms. Be patient shop around. Sellers know that you will offer less for a used gun than they are asking, don't disappoint them. On the other hand don't insult them either. I suggest you see what firearms are going for in your area. Common handguns like Glock are popular and turnover as new ones come on the marketplace. Go to the local library and consult the Blue Book of Gun Prices.
If you are a BUYER and acquiring a firearm to resell it through something like an estate auction keep in mind when bidding that there are often buyer's fees plus sales tax. In Arizona the average estate fee to the buyer is 15 percent plus 8.9 percent sales tax. Estate Auctioneers are required by both Federal and State laws ro collect sales tax and to get the firearm buyer cleared for purchase. If you have a criminal record don't bother bidding.
You bid a 410 Single Barrel Break Action Savage Shotgun for $100.00 you are all ready over the resale price and now you have to add 15% for Auction Buyer Fee and 9.8% Sales Tax making the gun purchased by you $126.27 total. You can buy a new single shot break action shotgun for around $150.00 to $160.00. These sell for between $70.00 to 100.00 used in good condition.
Also a good auction house will list the NRA Rating on any firearm they sell. Try not to bid anything under 85 percent condition rating unless you plan to keep it and use it yourself. Also many used guns come with issues like split or chip stock, rust, bad lever latch, broken safety, pitted bore, bad firing spring, etc. A gun smith is expensive so bare that in mind. The auction house at live auctions want to stir the bidders up and get them bidding against one another so they lose track of the price, don't fall for it.
If you buy a gun modified from its original use take a tape measure and make sure it fits the required ATF rules for both barrel and overall gun length.
If the seller looks suspicious don't buy a firearm from them it may be stolen or used in the commission of a felony.
Avoid buying firearms with a seller's ad like rare, collectible, in demand, great weapon I hate to part with it .... generally these are just advertising gimmicks.
Know your budget for purchase and stick to it. Shop for firearms within your budget range.
It's also advisable that you get some kind of Bill of Sale, preferable a Private Firearms Transfer Form completed by both parties.