I surely hope you arent going to wire the money to some online scam artist then try to go pick up your tractor. Tell the guy you will give him cash at point of pickup or better still go with him to his bank to present a certified check for the amount. The bank can instantly verify the funds, notarize a bill of sale and you are done.
I repeat DO NOT WIRE MONEY TO ANYONE TO BUY ANYTHING. DO THE DEAL IN PERSON, GET A BILL OF SALE THAT IS NOTARIZED FOR YOUR PROTECTION.
And get it in your possession as well. I always load up and strap down before the money/check comes out. I leave it in the glove box with the dog in the cab and she is very protective of her truck.