Personal residual income, often called discretionary income, is the amount of income or salary left over after debt payments, like car loans and mortgages, have been paid each month. For example, Jim’s take-home pay is $3,000 a month. His mortgage payment, home equity loan, and car loan are the following respective: $1,000, $250, and $200. Using a residual income calculator, Jim would calculate his RI to be $1,550 a month. This is the amount of money he has left over after his monthly debt payments are make that he can put into savings or use to purchase new assets.
P.S. I also fail to understand your fascination with real estate. Granted we’ve had some impressive spikes along the way, especially with once in a life time bubble we just went through. But over the long term (see Case Shiller real estate chart for last 100 years ) real estate tends to just track inflation. Why would you sacrifice stock market returns for a vehicle that historically hasn’t shown a real return?

To create residual income, you need to create something that people will continue to buy on a regular basis long after you’ve created it. A house is a prime example of this as people will continue to pay rent for the right to live in the house. A business needs to have products that are sold over and over again rather than trading the business owner’s time for money.

Quick question. I’m 21 years old and currently working full time (50 hours a week averaging about 12 dollars an hour. I was working 35 making enough to get by and save a little, but I read your post on the notion of working more than 40 to get ahead and decided a third job was best while I’m getting residency to get lower- instate tuition at OSU. So props, you had a direct influence on my life.)
You are also free to choose a fund that is based on any index that you want. For example, there are index funds set up for just about every market sector there is — energy, precious metals, banking, emerging markets — you name it. All you have to do is decide that you want to participate, then contribute money and sit back and relax. Your stock portfolio will then be on automatic pilot.
#9 Military pension/VA disability. Obviously requires a lot of front end effort in your 20s and/or 30s depending on length of service however once out and receiving it is totally passive with cost of living adjustment included most years. It has changed somewhat with new “blended retirement” plan but even those not staying past first or second enlistments often will get some VA rating. My wife got it on both ends of her service as the Navy paid for med school and then she was rated by VA after seven years active duty.

One aspect you might want to add to your scoring is “inflation protection”. At one end, bonds and CDs generally pay a fixed nominal coupon that doesn’t rise with inflation. Stock dividends and Real estate rents (and underlying property value) tend to. Not reallly sure how P2P lending ranks- though I suppose the timeframes are fairly short (1 year or less?) and therefore the interest you receive takes into account the current risk free rate + a premium for your risk. Now that I think about it, P2P lending probably deserves a lower score in the activity column than bonds too (since you probably need to make new loans more often).
I've got a $185,000 CD generating 3% interest coming due. Although the return is low, it's guaranteed. The CD gave me the confidence to invest more aggressively in risk over the years. My online interest income has come down since I aggressively deployed some capital at the beginning of the year and again during the February market correction. You'll see these figures in my quarterly investment-income update.
What I Do: I’ve set up multiple investment accounts outside my main operations bank that deals with working capital e.g checking, paying bills. By transferring my money to a couple brokerage accounts and two other banks as soon as it hits my main bank I no longer have temptation to spend on frivolous things. As a result, I can wake up 10 years later and reap the rewards of compounding. My 401(k) is the best example where constant contributions over 18 years has grown to over $500,000 without any savings pain given it just became a part of life. Real estate is also a fantastic asset class for the long term. It’s fantastic to enjoy your home, pay down your mortgage each month, and end up with a paid off asset that has likely appreciated during your time of ownership. 
Residual income is money that is earned on a recurring basis, typically as the result of a single original action. Rather than earning an hourly wage, residual income is typically generated through an initial investment of time or money with the goal of earning continuous payments. Once the initial investment, product, or service is made, the ongoing income that is earned is generally passive in nature.