I've posted about this before, but years ago I made a blog about completing the application and exams to obtain a professional engineering license in my jurisdi

I've posted about this before, but years ago I made a blog about completing the application and exams to obtain a professional engineering license in my jurisdiction. It is just a WordPress blog. Over a year or two, it started getting organic traffic since it provided information in an underserved niche. After making next to nothing with Google ads, I was approached by another site that sold help packages for the licensing process and we struck up an affiliate deal. It didn't work right away and had to build up, but nowadays it generates anywhere from $200 to $800 per month in completely passive revenue (haven't written a new post in years). The revenue has been growing too. It will have done about $5k in 2018.