When you sell Print-On-Demand items, you are selling products that aren't made yet. You create a design that you will be using on the product you want to sale. You list your product for sale and when a customer buys it, the company creates the product and sends it to them. You pay for product manufacturing cost only when it sales.Amazon, Redbbble, Zazzle, TeeSpring are some of the best platforms to start print on demand business easily.