If you are going to sell products or hosting services over the Internet/web, then there are chances that you will require some type of eCommerce solution. By e-commerce, I am referring to the features such as a shopping cart, SSL, and a merchant account if you want to process credit card payment. The shopping cart may only be needed if you plan on having a catalog of products available for sale. This makes shopping much easier on any potential customers.
If you plan on accepting credit cards, you will also need a merchant account. A merchant account is basically an account that allows you to process credit card payments from your customers and have the money deposited into your bank account. There are a number of merchant services available on the Internet, like Paypal, Moneybookers etc. Merchant fees range in price from $25 to $75 per month with setup fees usually in the $100 to $800 range. paypal.com seems to be the leader at a low price per month. Be sure to research companies before making a commitment.