In either case they are other's products and there are an enormous amount of possibilities. The key is to select both, the products and the companies that offer the best in their areas.
Offers cross the sky at every second, just fill some forms up and you will receive all type of business examples.
You can search for the topics you are most interested on Clickbank, Amazon or directly an the web by "products for resale" or "affiliate programs".
I have made many attempts on this line and I will tell you what I think are the good steps to be taken. MY COMMENTS HERE