Wait until it appears in PayPal and don't send if it is pending. Buyer may have used an e-cheque.

Only send when payment is cleared into PayPal.

If you are a new seller then you will have a 21 day hold on funds in PayPal.

But that is different to a pending payment.

Once cleared you send the item and you will need to wait 21 days before the funds can be accessed if you have the new seller limits.

Edit - Just checked and it appears you don't have new seller limits.