If you have a blog or other type of site, you can build affiliate links to different services on the website. Many people use Amazon as an affiliate partner. For example, if you are a beauty blogger writing about different products, you can set up Amazon affiliate links on your blog so that whenever someone buys the product you mention on Amazon, you receive a percentage of the sale. Amazon is not the only affiliate partner out there. Here is good, in-depth information on affiliate marketing. 
The appeal of these passive income sources is that you can diversify across many small investments, rather than in a handful of large ones. When you invest directly in real estate, you have to commit a lot of capital to individual projects. When you invest in these crowdfunded investments, you can spread your money across many uncorrelated real estate ventures so individual investments don't cause significant issues.
1. I started with doing tuitions , even after I picked my first work. Being in IT, I always had 5 days a week schedule but tuition/coaching is a time-tested way to earn clean money. I was teaching Mathematics to class X people. And if your pupil do good, like what happened when I was teaching this lady (in 1995) whose parents have given up on her, she was a in a plush school and I don't know what worked, she got such good marks that they hunted me down for a big pack of sweets after her X board exam, then that is extremely rewarding. You can start from your home, do evening class then move to a rented place and so on. It is very tiring but as I said, noone would short-change a teacher.
"For long-term savings, investing in low-cost index funds is the ultimate passive strategy," Goudreau says. "As legendary investor Warren Buffett recently told CNBC’s On the Money, 'Consistently buy an S&P 500 low-cost index fund. I think it's the thing that makes the most sense practically of all time.' By not picking individual stocks and, instead, buying a low-cost fund that tracks the market, you pay less in fees and take less of a risk. Then you can sit back and watch your money grow over time."
Most of us think of investment income as just the cash flow we get from bank interest, bonds, share dividends and property rents, some of which comes via a super pension.  But a more complete view is to also consider how growing the value of your investments can add to your spending potential.  This total return approach generates income from both income and growth to optimise spending from your portfolio across all market cycles, aligning cheap and expensive investments to your goals.