If I have one item for sale on a Paypal "buy now button", how do I stop two people from purchasing it at the same time? Is there some way to tell paypal there is only one available (without using a shopping cart? thanks.
Well, I think you can't. What you can do is have the person who are interested to email you then you generate a Paypal Invoice to the first person who email you and then when he pays, you tell the others it is no longer available. Alternatively, if you want to use the Buy Now button, you could refund all subsequent purchases once the product has been sold.