I have done it, but it ended up being a lot of work relative to what I earned (and eventually I lost all the income after a Google algorithm change.) The thing

I have done it, but it ended up being a lot of work relative to what I earned (and eventually I lost all the income after a Google algorithm change.) The thing is, it's generally easiest to create lots of value (and correspondingly, earn a lot of money) in an area where you have very little competition. 10 years ago nobody understood the internet, so passive income online was easy. 5 years later it was doable, but harder. Today you'll probably get a much higher RoI by learning R and doing some Data Science consulting.