umm, hows he pay for paypal without online banking.. ?
This tbh...
Your cousin is either dealing with a total mouth breather... (even without internet banking he can still phone his bank and make a payment to another account/sort code)
or (more likely) its a scam.
He could humour him on the off chance its not a complete scam... tell the buyer to use the telephone... explain to him in simple English that he can still phone his bank and wire him the monies without using paypal.