Have buyer escrow the payment with an atty. (preferably your atty).
Write up terms of sale.
Once atty. has cash in hand (not a check, not an I.O.U.), do
electronic transfer of ownership.
Atty / Buyer has 3 days to confirm complete and full access, done with whois and ability to change DNS etc.
Atty. sends cash.
This process happens at escrow.com, they are handy if you don't have an atty. easily available. They change a percentage of the sale.
There are lots of things that could go wrong with this scenario. You have to have basically honest and willing parties on both sides of the transaction.