How do I build a trading site?

I want to build a trading site for a specific video game so players can trade their items in an organized manner through this site…
here is an example: www.nookbay.com
I want to do the same thing just like that website but with a different game. What can I do? How can I set it up to look something like that?

That site looks like it’s running on http://www.phpprobid.com/

Hi,
You’re going to need some sort of auction software, as suggested above. PHP (a server language) is probably the best thing to use, as it will allow you to scale up your site pretty quickly.

you can also check out site such as rent acoder and scriptlance if you want people to build it for you