2) Assuming you don't live in a Nazi state such as NY, Kalifornia, New Jersey, etc., under federal law you are limited to a face-to-face sale to another resident OF THE SAME STATE THAT YOU RESIDE IN.
3) You CANNOT SHIP THE HANDGUN TO THE SELLER. You must perform the transaction face to face with the buyer.
4) Again assuming you live in a free(er) state, you can sell your handgun face to face to someone at a gun show.
5) After all of that hassle, you might just be better off selling it to your local gun store, or using it as a trade-in against the new gun you want.
Obviously, a transfer of a handgun across state lines requires a dealer to be involved.
I'm sure you meant "buyer",,,,