Quoted from PNorth:
1. Create a new bank account.
2. Have the buyer go to a branch of your bank and deposit CASH into your new account.
3. Transfer the funds into your regular account.
4 Close out the new account.
If the buyer deposits cash into your account, they can't withdraw it back, and the bank can't hold it. Safest, least expensive way of doing it from my experience.
When I purchased my TWD this is what the seller did.