The first thing you need to do is read the rules and take the time to research the forum.
There are expectations before you can use the Buy/Sell Marketplace.
2 helpful links :
http://www.thehunterslair.com/topic/14054-so-you-want-to-makebuy-a-predator-suit-read-this/
http://www.thehunterslair.com/topic/15093-before-you-sell-please-read-first-bst-rules/
You would also be best served to introduce yourself as well :
http://www.thehunterslair.com/topic/20822-new-members-introduce-yourselves-here/
The is a great place but you will need to take it upon yourself to take the time to read as much as you can, ask questions and follow the protocols.
Everyone is willing to help but the folks who come on and don't understand the costs and times associated with either building or buying the components for a build, will draw the ire of a lot of members. Don't be that person!
Good luck!