We usually only recommend that you ONLY sell products that are already listed and being sold on Amazon because it greatly decreases the risk, cost, and time/skill associated with selling on Amazon.
Products that are already on Amazon are much less risky because you can look at sales history and estimate how much you will sell and how much you will profit before you invest in the product.
New products have no history so it is very difficult to estimate how quickly the product will sell or how much you will profit. For new products, you also need to build optimized product listings with descriptions, pictures, etc. which will cost you more time and money. So, with a new listing, you would have to create the listing yourself, and then market and advertise in order to drive traffic to the listing.
