The idea of long term residual income is a powerful one.  Who does not want to do work once and reap the benefits for years to come. The sad reality is this idea is used to convince people to join a business opportunity that can’t provide long term residual income. Don’t waste 3-5 years of your life for something that you will not find in a MLM scam.
Managerial accountants define residual income as the amount of operating revenues left over from a department or investment center after the cost of capital used to generate the revenues have been paid. In other words, it’s the net operating income of a department or investment center. You can also think of it as the amount that a department’s profits exceed its minimum required return.
Investing in rental properties: Another form of real estate investment, rental investments (i.e. becoming a landlord) could steer you down the passive income path of steady monthly rent checks that you can use to pay off a mortgage loan on the rental property. After the mortgage is paid off, those monthly checks go right into your bank account -- potentially for years to come. 
This equation is pretty simple and incredible useful for management because it looks at one of a department’s key components of success: its required rate of return. This component helps management evaluate whether the department is making enough money to maintain, close, or expand its operation. It’s essentially an opportunity costmeasurement based on the trade off of investing in capital in one department over the other. For instance, if management can invest company revenues in department A and earn a 15% return, department B would have to make at least 15% in order for the management to consider the investment. If department B doesn’t meet minimum 15% return rate, it might be shut down or redirected.
Add Leverage (Mortgage) and you greatly increase the ROI especially from the perspective of using Rents (other peoples money) to pay down the mortgage and increase your equity in the property over time. At this point then yes price appreciation is secondary bonus and we have an arguement of how and why Real Estate can be better than Growth Stocks in some scenarios and for some investors.
Being able to generate passive income largely depends on your audience, and if they detect that you care more about making money than serving them, you won’t succeed. “Whenever I’ve seen people do something just for the money, they’ve failed because their intentions aren’t driving them in the right direction. It should always be about helping people and about the passion of making others feel better. The byproduct of doing that is generating money,” says Flynn.
Good ranking FS, I’d have to agree with the rankings. And it looks like your portfolio covers five of the six! Some people consider real estate passive will others classify it as active. But every scenario is different, whether you are doing all the maintenance and managing yourself, or you are contracting out a lot of the work. Obviously it takes a lot more time and effort than purchasing a 36 month CD and “setting it and forgetting it.”
Whether you take a “distribution” (aka free-cash-flow) in the form of a dividend, interest payment, capital gain, maturing ladder of a CD, etc, you are still taking the same amount of cash out of your portfolio. Don’t fall for the trap of sub optimizing your overall portfolio’s performance because your chasing some unimportant trait called “income”.
Residual income can have two different definitions or applications. The first definition, a less common application of residual income, is the money that is left after monthly debts are paid. This calculation is particularly important when a person is seeking financing or a loan based on their income and available money to cover the additional debt. In this scenario, the residual income is calculated by this formula: