Quality
no
Yes. If you lie on the 4473 and get caught.
Gun shop/ gun show
It really depends on the Manufacturer, what model gun, and if it is used or brand new from a store or from the Manufacturer. Look at prices online prior to buying a gun. If you have a gun and wish to sell it, I might recommend taking it to a pawn shop and have it valued. Or you could even just take the highest offer you can get.
No money, no gun shop nearby, felony conviction, underage
The cast of Buying a Gun - 1929 includes: Charline Burt George Burton Lupino Lane Wallace Lupino
It MUST be made specifically for an air gun.
The Freedom Group.
If selling the gun is banned, then buying it before the ban is no problem. If owning the gun is banned then it does not matter when you bought it.
A good dealer. Your question is too broad to give a specific answer- that would depend on the type of gun. However, a good dealer will examine used guns for problems, wear or defects- and help guide you in your purchase.
"Best" is a relative term. Talk to a good gunsmith.
You can't look in your gun in any halo.