I never was the entrepreneurial type. But after losing my job as an audio engineer in 2009, I had to get creative to make ends meet. Thirteen years later, at age 39, I’ve built two online businesses that earns me a combined $160,000 a month in passive income. I also recently published a book, “How to Get Paid for What You Know.” The first business I started was The Recording Revolution, a music and education blog that sells music production courses. The second, which I started in 2018, teaches people how to make money off their passions, like I did....