It has Fraud written all over it.
He will pay you the 10 grand via paypal. Then he will come in person to your door and after that he will tell paypal that he never received the 20p, so paypal will lock your account and you are in deep sh#t.
He will pay you the 10 grand via paypal. Then he will come in person to your door and after that he will tell paypal that he never received the 20p, so paypal will lock your account and you are in deep sh#t.