Build an Online Store

Here are the details of the project I require: 1) I need a database and reporting area for customers who want to sell items on my Web site. As can be seen here: [login to view URL] There is a link that says, "Have one to sell, click here?" I need this link to be a button whereby a returning customer logs into their account and adds this item to their database of products for sale. If the customer doesn't have an account they will be prompted to create an account. This would be the same as "Have One to Sell, Sell On Amazon" as can be seen here: https://www.amazon.com/Playboy-Magazine-January-Pamela-Anderson/dp/B0021PGEHU/ref=sr_1_1?ie=UTF8&qid=1467829025&sr=8-1&keywords=playboy+january+1996 I also need a platform so that sellers can upload digital products to my Web site. They would then be able to sell them and there would be a reporting area where they could see what they have bought and sold. I also want a platform that would feed their inventory into both Amazon and eBay, so that they would only have to list their inventory in one spot, on our Web site and this inventory would deplete on all platforms as soon as it sold on one of the three sites. I don't want to use WordPress or Magento or any other Content Management System. I want all of the code written in PHP/MySQL with lots of comments lines so that I can follow what is going on.