If your original listing says paypal on it then you have to accept it otherwise ebay will suspend you or ban you pemanently, not to mention if the buyer puts in a complaint then you will also have a non performing seller violation as well as negative feedback.If your original listing has another payment method(paymate/merchant credit card) then you are fine-cash on pickup is not enough-someone can even pay you by paypal for a pickup item(you would be really stuffed then)