Joey could actually put a stop to most of this nonsence with a simple disclaimer at the top of each Sale category.
" All transactions must be settled in full within 30 days of payment, or seller will be permanently banned from placing any further For Sale ads"
With that, all the seller needs to do is show a screenshot of the PayPal transaction or pic of cashed check (SOL on money orders) and a PM to the seller on the 30th day.