When your store grows in size, you will need to accept credit card.

And you will need to to have a payment gateway to link your site to the merchant facility provider.

A very popular payment gateway is eWay.

the script is here - free download:
http://addons.oscommerce.com/info/6014
The price is to install and co-ordinate the process, as you will need to launch eway application, SSL install, and configure the module once everything is in place.

This service is for osCommerce and Easy Webstore only.

SSL price not included.