To integrate a shopping cart into one website, cart software must be installed, then connected to a payment gateway. An article about shopping carts recommended a company called digiSHOP. This company is expensive but the writer explained that it was easy to use and customize.

Personally, I tried Zen-cart and it was much too difficult to work with. I spent hours reading and trying to figure out the code without seeing any progress. Although Zen-cart is free, I would pay for it in hassle.

Once the shopping cart is established, then comes the expense of a Merchant Gateway or Payment Processing. The industry standard is Authorize.net for accepting credit cards and placing the funds in your account. Bottom line, if a person wants an ecommerce site, it will require a fair amount of money and a designer.

Easier payment solutions would be PayPal or Google Checkout.

Additional Research:
intelli-collect
2 check out
click bank

company w/ merchant accounts
merchant warehouse
insta-merchant
durango merchant services
merchant express