Software Site Script

Looking to have a PHPmysql script for a Software salesdevelopment site. This is the first project on this site, there will be more to come. This script should just have the ability to add software for viewing (Meaning description, features, screenshots, price etc ). It should also let customers purchase the items through PayPal (Other payment methods are in the works). I have most of the design done, just looking for modules to stick in. All Items should be able to be edited through a Web Back End. Other Projects in the future will be: Customer Account Login Software Version Check (More to Come as Site Grows)