No way would I accept 20k cash, unless it was at a bank who accepted it as genuine and deposited it on the spot. Even so, why would this guy want to travel around with that? Cashier's checks are perfectly OK. The check is made out to you. You call the bank before hand and confirm that the funds have been set aside to honor the check, and that only the bearer of the check can get the money. When I bought my car, I had two checks, one for the seller, and one for the financial institution holding the lien. The seller got his check, we jointly went to the post office and mailed the 2nd check, and he signed a bill of sale confirming the sale to me. The bill of sale was an official Indiana State doc. This is needed because he does not have the title, the loan company does.
I also confirmed with the finanacial institution what the payoff was on the loan, so the check would release the lien. Once the lien was released, the title was mailed to the seller. The seller then signed it, and sent it on to me. There is an element of trust involved on the buyer's part. But the seller had confirmation that the checks were good, and the title does not get signed off until the money is in hand.