I want to make a website like etsy and ebay. People have

I want to make a website like etsy and ebay. People have to be able to sell their products by making a log-in and creating a product. I want this "create a user" interface to be as simple as possible and making the creation of the product very simple. The idea of our site is that people only add one product of same kind. Therefore there is no need for SKU and inventory tracker. Is there a way to get rid of all this and make the interface a lot simpler? Also the products which are going to be sold are quite unique. Therefore I want the seller to be able to choose from a list of categories to sell under, and not being able to make their own. Is this as well possible?

Regards Philip