I'd use Moniker's Escrow service.
Usually the escrow service asks who you want to pay the fee. It is btw you and the buyer/seller who ends up paying it.
If you were selling a domain, you would go to the escrow site to start the transaction. You would submit your info, the other party's info, select who will pay the fee, and answer a few more questions. From there you will both be sent a form (at Moniker anyways) where you both need to sign and send back. This is a legal agreement. Other party submits domain/cash, you submit what you need to and it goes from there.