If your buyer has a Godaddy account, I think you can just "push" it to their account very easily.
If they have an account with another registrar, then they would have to request a transfer and pay for it, then you would have to approve the transfer so it went to them.
I discovered that I could NOT transfer my .ws domain from Godaddy, so you might run into problems. The best thing is to contact Godaddy and get them to help you. Their support is very good.