As an addendum to my series on internet commerce without a website; I need to add one more tidbit. If you are accepting payments through Paypal, know that Paypal is also owned by eBay. If your buyer, right or wrong, has a problem with the product---anything from buyers remorse to didn't read the listing or store policy, and the buyer invokes the "isn't as described" clause; the amount of the sale is put on hold.
This occurs even when it is past the returns are accepted time as indicated in writing in your store policy. This occurs even if the money is not in your Paypal account---remember Paypal has access to your bank account or credit card.
eBay then apparently acts as judge and jury in the case. The internet is full of angry, frustrated, and disgusted sellers who have been cheated out of the merchandise and the money. In contrast, rarely do you find a disgruntled buyer.
Beware of this pitfall when merchandising on eBay. As an eBay staff member put it "if you don't like or agree with our policies too bad don't do business here."
And that is indeed the kind of customer service you can expect whether you sell $1 or thousands of dollars.