Build a list in a particular niche and tell them stories. Create a bond. Build a relationship with them. It's important. Then, when you've created a bit of culture, start marketing affiliate products or services to them that you think they might like. Just be sure that you personally vet out whatever it is that you're selling to avoid complaints if the product or service falls short.
My goal with this site is really only to write about 25-30 pages with information as I learn about boats and do customizations to my boat. I’m also adding a forum. Forums seem to be very popular with boat owners so I’m anxious to have others generate content for me. I don’t have huge plans for this site, but I’m sure it will bring in a few thousand a month if I don’t fizzle out. This is going to be my fun project for the next little while.