I thinks there so many links or previous topics in re buying  or selling goods on market place,all you can do is to explore those links in the google or just try to find that in the wikepidea.buying or selling good with payments of bitcoins in the market place required a legalization because its refers also to which country you belong so that you can trade goods without hazzle from the government,just like in the japan they are free to make a business using bitcoin as a payment in exchanges of goods because they are legal.