You don't need a product to sell to make money. My fitness site only offers information and I make money from AdSense and referring people to books and videos on fitness.
With AdSense you are helping Google advertise by displaying other advertiser's ads. So any time those ads get clicked you earn money. So no product involved.
So let's say you go with my idea. You could join Adobe's affiliate program through
www.cj.com and refer people to buy PhotoShop. Anytime someone clicks on your link to PhotoShop and buys from Adobe, they credit you a commission through cj.com and CJ pays you.
I've never had any products to sell and have always created information only sites and made my money through affiliate programs like I described above and AdSense.