any site to get opencart extensions for free?

If you used Drupal or Wordpress or any other content management system, you'd design the site and integrate a shopping cart or ecommerce solution. With OpenCart, you're doing it all in one. In addition, OpenCart has features that easily give you information you need to manage your business. It looks like your computer guy is doing you a favor in that regard. He may be using WP for your mini sites if their purpose is to channel traffic to your main site. For people who know what they're doing, WP sites are easy to build and maintain. They're definitely real sites and you'd probably be surprised at the sites you use that are built on WP. The platforms you've mentioned are used for dynamic sites and use PHP. PHP sites can be attractive to hackers, so be sure your guy is taking all possible precautions to make your sites secure.

i meant paid extensions for free

in opencart extensions site, there are some extensions is free

http://www.opencart.com/index.php?route=extension/extension&filter_license=0