Focus on your primary passive income stream first. It's difficult to grow your passive income into multiple streams if you don't already have one, solid stream. Focus all of your efforts on that one project first and help it grow as productive as possible. Then, you can take the money you've made and lessons you've learned from this passive income stream and put them into others.

The more residual income you can build, the better off you’ll be. In fact, it’s said that the average millionaire has 7 different streams of income. By creating passive income streams that generate money while you sleep, you’ll build wealth faster and diversify the ways you’re able to make money – which helps protect you from the loss of any one individual income stream.
Rentals, just like stocks, throw off cash. With rentals we call that cash “rent”, and with stocks we call it dividends. A significant difference however is that the S&P 500 has appreciated at ~6% per year (above inflation) for the last 100 years…..Real Estate has had almost 0 growth above inflation. So are rents higher than dividends? Maybe, maybe not. But unless you got one heck of a deal, the delta in rent over dividends will have a very tough time making up for the 6% per year difference in appreciation.
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.