If you gain some traction, there is ad revenue to be gained. I have found even 100 to 300 page views a day is enough to start seeing a few dollars each day. B2B ads pay out more. I've seen single clicks bring in $5+. Once built, not usually much you have to do after that, and they will typically grow slowly over time. And I feel good about them, because I know businesses are getting actual value out of them.

I have not struck the right chord with affiliate revenue yet. But I know there is money to be made with the right niche. I think you need to be a little more invested in affiliate sites, and have a real interest. These sites seem to require a steady flow of new content, though you may be able to automate some of it.