If an investor puts $500,000 into a candy store with the agreement that the owners would pay the investor a percentage of earnings, that would be considered passive income as long as the investor does not participate in the operation of the business in any meaningful way other than placing the investment. The IRS states, however, that if the investor did help manage the company with the owners, the investor's income could be seen as active since the investor provided "material participation." 
I have to agree. Our Duplex cost us 200k initially in 1998. Over time and completely refurbishing the property with historically appropriate sensitivity, we invested another 200k or so. We just had a realtor advise us we could ask 700k for it today. It nets us 30k annually after taxes, insurance and maintenance. We still have a loan on it which I have not taken into account, that will be paid off within 5 years if we keep it. My mental drama now is, while I am quite giddy over the prospect of earning a tidy sum of profit if I sell, what then would I do to equal the ROI and monthly income this thing generates? Rents are low, they should be 4k a month and will only go up. Tempted to keep it and not sell. And while I do have some stocks, I basically suck at them. I am much better at doing properties.
I invest about 5% of my pre tax income in 401k that my employer matches. Have close to 70k in cash in checking. Also,I liquidated around 40k in my 401k and not sure where to invest that in (bonds vs stocks) because of stocks trading at record high. Have a rental property that is paying itself now and I will pay off the mortgage completely in 5 years. My immediate concern is the cash in checking acct that’s not doing much. Thanks for your reply and appreciate your work. I am learning a lot

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.