While it is important to find something that you love to do and turn it into a money making business, you do have to be cognizant of the return as you pointed out. There are many opportunities that I found and tried out that at the time seemed great. But when I took a step back, I realized that I was working a lot for very little income whereas other things I love doing brought in much more money.
One great way to generate a passive income is through affiliate marketing. Now, this does depend on the size of your list. Yes, size matters when it comes to your list. Especially if you're looking to make some serious money and do it on autopilot. But, list-building takes time. It doesn't happen overnight. And you need to add value to your list or you become obsolete.
It’s been almost 10 years since I started Financial Samurai and I’m actually earning a good income stream online now. Financial Samurai has given me a purpose in early retirement. And, I’m having a ton of fun running this site as well! Here’s a real snapshot of a personal finance blogger who makes $150,000+ a year from his site and another $180,000 from various consulting opportunities due to his site.
Diversify safely but DIVERSITY. You do not need to get the best and highest return all the time. If so, you are not earning passive income you are earning active income which is taxed differently (see IRS.GOV passive -vs- active income definitions). As an investor you do not need to be chasing ‘the almighty dollar’. This is a losing proposition. Make the dollar come to you.
If you're looking to get started in real estate, look at a crowd funding solution like RealtyMogul. It works similar to LendingClub - you commit as little as $5,000 towards a property. When the property is fully funded, you become an owner, and will receive your share of the earnings and appreciation in the property.  Check out RealtyMogul to learn more. 
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