If you're using an Internet business to earn extra income-or maybe even a full-time income-you will definitely need to take credit cards. Checks may work just fine with a brick-and-mortar retailer, but when it comes to an Internet business, most online customers have little patience with mailing in a check and waiting for the business to get it before sending in their order.

So before starting up your extra-income-generating Internet business, take a look at your options for accepting credit cards. Here's a quick breakdown of all the ways you can accept credit cards online.

PayPal. PayPal is one of the most common and easy ways to accept online transactions. The program will send you an email when a payment goes through, and you can transfer the payment to your account electronically-it will usually take 3-5 business days to go through. PayPal has relatively low transaction fees: around 2.9% at the time this article was written, plus 30¢ per transaction. Its drawbacks include the fact that it is not a federally regulated bank, and some users have reported negative experiences with the service; it may seem a bit amateurish for some companies to accept only PayPal (although some customers prefer it); plus, customers have to open their own accounts to use it, which they sometimes resist.

Verisign is a competitor of PayPal's. They charge a flat monthly rate to join, plus a lower transaction fee than PayPal. If you're charging a higher volume of credit cards, Verisign is probably a more cost-effective choice for credit card transactions.

A bank merchant account. Merchant accounts are typically the way most companies choose to go when they have started to make more than just a little extra income. Fees vary depending on your bank's policies. This option is typically more work than using PayPal. Once you've set up a merchant account, you need to put script on your website that allows customers to pay your account using your credit card. You also must buy a credit-card processing service. Most importantly, you must make sure your website is secure so that your customers' credit card information cannot be stolen. To accomplish this, you must set up your website with SSL (or Secure Socket Layer) technology. Much of the time, your ISP can handle this for you.

Digital information payment providers. These services, like PayPal and Verisign, allow you to accept credit cards without a merchant account. They tend to be much more expensive than the PayPal-type companies, but they also give you more-Clickbank, which charges a $49.95 activation fee plus a 7.5% transaction fee doubles as an affiliate marketing program, where you can earn money by advertising products through your site. Digibuy, which charges a 13.9% transaction fee, also gives you invoicing, a shopping cart program, and test orders, among other services.

An account with a major credit card company. Major credit card companies such as Discover and American Express have merchant accounts available for businesses. Not all credit card companies offer this service, however; MasterCard, for example, requires that you have an account set up through a bank to process their cards.

An Internet business is a great way to generate extra income. And you'll need to accept credit cards in order to make it happen. Studies indicate that customers spend over 30% more on average with a credit card than without one; online, they'll spend much less without a credit card. Accepting them online is the only way to make your Internet business viable-but with the extra income you generate, the fees will definitely be worth it.