Sell your own products
There are many different internet marketing products available online related to every topic you can imagine and some will offer resale rights, master resale rights, or private label rights. Those products that come with resale rights allow you to sell them on your own website and keep all of the profits.
Those that offer master resale rights allow you to sell the rights to the product as well as selling the product itself. But for the most flexibility, private label rights give you full control over the product so that you can add, change, and repackage it to make your very own product.