While looking into passive income streams for someone with a Science/math/Engineering/Programming background, I ran into various ideas. I was looking to generate a passive income that would not take too much of an initiall learning curve. And it occurs to me that teaching/writing books/ on High School math/Physics/English is something I can do without a lot of prepwork.

I am in Toronto . what are the average income opportunities for something like this? Where should I start looking?