However, with passive income, there is not a direct connection to time involved. Once the original work is completed, the income continues to come in as long as demand for the product or service exists. Each time a song is downloaded, the musician receives money as a passive income. They did not have to record the song again or do additional work for each download, yet they are paid for their original work.
Secondly – and this is just quibbling – I’d change that risk score. The risk of private equity is incredibly high and should be considerably riskier than bonds! You are providing a typically very large amount of capital to one business that you agree to have no control over, and the success or failure of that business over a locked, predefined term determines your return. And in the few deals I’ve negotiated for clients, my experience has been that there are often management fees, performance fees, etc. that may cut into your potential gains, anyway. You’re putting a lot of eggs in one basket, and promising an omelet or two to the management no matter what. You really need to be confident that you found the next Uber before you take this giant risk!
The main advantage of the residual income metric is that it measures excess return earned by a department in absolute terms. A positive residual income means that the department has met the minimum return requirement while a negative residual income means that the department has failed to meet it. Return on investment (ROI) is another metric which measures return in relative terms.
The vast majority of people imagine working a forty hour week, and then earning a pay check for the job they have done. That is, in fact, how most people support themselves year after year. But did you know that it is possible to continue earning income even after you stop working. Creating a stream of residual income might be something you want to take a look into and get some more information on. 
Many people talk about passive income and create the impression that you never have to do anything to keep that income going. The truth is that you will normally have to keep your eye on things if you want it to run smoothly. For example Richard Branson doesn’t run any of the 400+ companies he started but he goes over the numbers each day to make sure they’re performing well and calls the CEO if there are any problems.
I wanted to specifically call out one particular strategy within equity investing that bears mentioning – dividend growth investing is when you focus on stocks that not only pay a dividend but have a history of strong dividend growth. When I was first building my portfolio of individual stocks, I focused on buying companies with a history of dividends, a history of strong growth, and financials that supported a continuation of both.
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.

One word of advice, and something I intend to do once I have the money saved up, is to build or buy out property that can support apartments or townhomes. One tough mistake some people make is buying a pair of homes to rent out and they get a nice $2,000-$3,000 a month but that’s it. Buying a house is expensive and the rental prices keep lower income families from potentially coming to you with their money to rent. If you have an acre to work with (more or less is OK too) you should be talking to a contractor to build apartments or townhomes. You will make a little less per unit BUT your audience grows significantly because now you can have college students, single parents, older folks, etc. all able to afford your rental units AND instead of capturing one $1,000-$1,500 a month payments, you can probably charge $700 a month per unit (or more, depending on the market) and build maybe 3, 4, 5, 10 units for the price of a home or two and now you’re making something like $2,100-$10,000 a month. It all depends on what you have to invest but if you’ve got $250,000+ I’d highly suggest you talk to a bank/investor that can get you in touch with a good contractor to build on a property and get permits and take out a matching $250,000 loan (I’ve read that $500,000 is plenty to build a good amount of apartments to start) and you can fill up your apartments and make a killing every month. You’ll have more tenants to deal with but if you’re competitive with your pricing you won’t have a hard time keeping tenants or replacing them.