A simple solution is to tell the seller that any freight company coming to pick up the item must pay 100% of the amount in cash and you will refund his deposit via PayPal. No cash, no sale.
Other things you can do is offer to ship to his verified PayPal address. If he doesn't have a PayPal account but is using PayPal for payment that is another red flag. You have no protection when payment is via friends & family. I would rather lose 3% or 3.5% (Whatever PayPal is charging) by issuing an invoice and being paid on the invoice and have recourse than lose it all. Then only agree to ship to a verified PayPal address with buyer paying shipping and PayPal fees.