What you need are credits. You can get credits by listing your own things and selling or you can buy credits etc. you can read about Listia. I suggest you try that. :-)
Huni, read the rules , you will get the idea !! with credits if you win the auction its yours, if you place credits in the first place & won, if your won a auction , make sure you have a listia address, you need that so people know where to send your item, that you won, if you do not have an address you need listia's approval before you can participate !! where you have to pay for shipping, then yes the cost of delivery as you already paid for the credits,
Its that simple, obviously you need to get listia's approval before you can be part of listia,it sounds to me thats what you need to be, as otherwise you are not legit !!