12 years ago, I built a site I had absolutely zero intentions of making money from. I had an interest in an upcoming video game, and thought it would make a perfect mate for an online community. So I reached out and found a talented guy online that was also interested in the game and also had the skills that I didn't (web design), and in a couple months, we launched.

After about a year or two, money became a necessity: the popularity outgrew the free bandwidth, and I was forced to find paid hosting. So I started accepting donations. But that wasn't quite enough to cover the costs, so I added ads to help supplement the donations.

But surprise, as the popularity grew, the revenue generated from the ads and the donations coming in started to largely outweigh the costs, and now I'm making a pretty decent passive income from it.

I could easily scale back to just donations now, but since the ads are there and pulling in quite a bit (for a site mostly on auto-pilot), I have no intentions of scaling back.

(I will say, though, that I don't go to the extremes that most do to monetize their site. The ads are only in the forum area of the site, and are only in two to three locations. No interstitials, no videos, no popups/unders, etc. And they're located at the top, bottom, and right vs. right in the middle of the content. Pretty much anything that would annoy me (banners don't annoy me) I keep off the site.)

I'm not saying the OP is making money out of necessity, but just that I understand going into something with the intentions of it just being a fun side project, and then later realizing the potential of making money from it.