on 08-06-2012 07:13 AM
PO Boxes are commonly use for the purpose that you are just mentioning. Most Sellers use the USPS service to deliver your package. If you run across a seller that advertises UPS service you will have to provide them a streets address prior to paying for the item. No problem.
on 08-06-2012 07:30 AM
Set up two different address destinations in your Shipping Addresses List... one for your street & one for the PO box.
When you go through eBay's checkout system to pay, you're given the opportunity to select which address you want the item shipped to.
If the seller has quoted UPS or FedEx, you must use your street address.