We have someone who is traveling almost three hours to look at buying our RV and Truck. The total price will be over $100,000. What are the safest methods of payments that we should accept? Any other advice to prevent getting scammed?
CASH! Go with them to a branch of their bank and get cash and deposit it in your bank.
or
Have them wire transfer the money to your bank.
or
Go with them to their bank, have them get a cashier’s check, then go with them to your bank and deposit the money in your account.
Don’t sign the documents giving them ownership until you complete one of the above.
A bank branch isn’t going to have $100,000 in cash. The other two methods suggested are good.
You can get cash with notice. But a wire transfer or cashier’s check from the buyer’s bank, with funds validated on the spot makes more sense, and is as good as cash… almost. 
Cash only. And do the transaction at your bank so you can get a notarized bill of sale from the buyer plus cash payment and immediately deposit the cash.