To echo all the other posters, use PayPal to start off with. If you are asking for basic guidance on SSL certificates you obviously are not prepared or in any position to set up your own secure payment site and meet the many security requirements.

You can also use other payment systems such as Daopay and Worldpay which you could never duplicate.

You would need to be doing many tens or hundreds of thousands of dollars a month in sales to justify doing your own ecommerce site and the cost of setting it up and operating it, so you could save a percentage or two on the discount rate.