You will need to consider the payment options that you want to offer on your ecommerce website.
Here are some of the options and issues:
Cash on Pickup
EFT to your bank account
Offline Credit Card – capture the credit card details and then process them manually.
Online Credit Card – process the credit card online – this can be done directly with the banks payment gateway or through a third party provider.
There are fees and charges that will be charged on some of these options by the provider eg paypal or merchant fees. You need to have a clear understanding on what you will be charged. Banks usually have conditions that your business and website must meet to be able to use their service.
If you are going to process credit cards then make sure you have a SSL on your website to ensure that the information is encrypted.
Most new sites start with a few options eg paypal, EFT and cash to keep it simple. Paypal is widely used and trusted worldwide and is simple to setup.