It's wise, if you are offering something to be collected, to insist on cash and not accept PayPal payments, whichever site or medium you sell on. A common scam consists of paying on PP, collecting the item and then clawing back the payment on the grounds that it has not been received. As the seller has no proof it was collected (getting someone to sign a receipt won't necessarily protect you because the buyer can easily claim it's a forgery) and PayPal is well known for siding with buyers, you can end up empty-handed.