Bollocks to accepting a paypal payment for someone is collecting. You realise that the buyer can open a dispute with paypal claiming you never sent him the item, as he collected you will have no tracking number to prove to them the buyer has the item you sold.

You are potentially leaving yourself open to lose the money that has been paid to you.

Paypal hold funds for 21 days when they deem you to be a high risk, it is in an attempt to protect the buyer from fraudulent sellers.