I make a little bit of money off of referring people to services I truly believe in. I never recommend things I don’t personally use, but if I’m going to refer friends to Shopify, products on Amazon, or Udemy courses besides my own, I have no shame making a couple bucks off it. In most cases, these referral sales come from older links within my podcasts or courses, and therefore, are completely passive. 

In 2012, even I wrote a 150-page eBook about severance package negotiations that still regularly sells about ~35 copies a month at $85 each (2nd edition for 2017) without any effort. In order to generate $2,975 a month or $35,700 a year in passive income as I do now, I would need to invest $892,500 in something that generates a 4% yield! To earn $10,000 a year in passive income would therefore need roughly $250,000 in capital.
We are going to start with 1.5 years of all spending needs in cash. We will draw 1800 to 1900 per month. We will add to this from the index funds by taking a portion of the gains in good years to supplement. This is the total return portion of the equation. Obviously, if stocks decrease drastically over a 5 year period, then I would have to reload by selling some of the ETF holdings.
If you have specialized knowledge in a certain topic, you can put together an online course to teach others. For example, if you have experience in real estate investing, you can create an online course “Real Estate Investing 101”. The benefit of an online course is that once you create the course material, you can sell it to as many people as you want.