Require a SCRAP(WASTAGE) Buying and Selling WordPress Website

I need a SCRAP(WASTAGE) buying and selling wordpress website like the following sample websites. Please have a look. [login to view URL] [login to view URL] [login to view URL] [login to view URL] [login to view URL] [login to view URL] For scraping there are 2 kinds of site can be developed. 1st one is (In the all above sample sites) the site admin directly purchase the scrap from customer and later sell those scraps to another buyer. In this case website admin require capital to purchase it and require warehouse to store those scrap. There two are the most risky point from the point of view the website admin. 2nd one is inside one site there will be the collaboration of scrap buyer and scrap seller both. Once seller are ready to sell at the same time buyer will purchase those scrap. There will be a rate chart in this site. Based on that rate chart buyer and seller will buy and sell those scraps and between this transaction admin will generate commission. In this type of site major advantages is admin should not purchase those scrap that's why admin do not need capital to purchase it, as well as though admin is not purchasing those scrap that's why it is not needed to store those scrap by the admin. Now as a website developer you please suggest me from the above two types of websites which website will be COST EFFECTIVE AND LESS EXPENSIVE TO BUILD, PLEASE NOTE THAT I HAVE LIMITED BUDGET FOR THE SITE AND I WILL LAUNCH THE SITE AS ON ''TEST DRIVE''.