You should also offer options for folks who don't want to use their credit card. Allow them to print out your order form and fax it in. Let them call in their order. Or let them place their order online, but do the credit card part by phone. You can sell advertising.
Advertising is audience delivery.
If you get lots of visitors to your web site, or if you get many visitors of a particular kind, then other businesses may be willing to pay to use your site as a way to reach your visitors. Remember that the best ads, for you, for your advertisers, and your visitors are content ads. Let advertisers provide an article or other form of information that helps your visitors solve a problem or answer a question they're likely to have. Then link to the advertiser from the content. You can have memberships or subscriptions.