As an economic concept, residual income has a long history, dating back to Alfred Marshall in the late 1800s.1 As far back as the 1920s, General Motors used the concept in evaluating business segments.2 More recently, residual income has received renewed attention and interest, sometimes under names such as economic profit, abnormal earnings, or economic value added. Although residual income concepts have been used in a variety of contexts, including the measurement of internal corporate performance, this reading will focus on the residual income model for estimating the intrinsic value of common stock. Among the questions we will study to help us apply residual income models are the following:
There are three main categories of income: active income, passive income and portfolio income. Passive income has been a relatively loosely used term in recent years. Colloquially, it’s been used to define money being earned regularly with little or no effort on the part of the person receiving it. Popular types of passive income include real estate, peer-to-peer (P2P) lending and dividend stocks. Proponents of earning passive income tend to be boosters of a work-from-home and be-your-own-boss professional lifestyle. The type of earnings people usually associate with this are gains on stocks, interest, retirement pay, lottery winnings, online work and capital gains. 
That is a nice list of passive income sources. Actually, the most up-to-date list of dividend growth stocks is the list of dividend champions, maintained by Dave Fish. The list of dividend aristocrats is incomplete at best. For example, the dividend champions list has over 100 companies that have managed to increase dividends each year for at least 25 years in a row. The list of dividend aristocrats has no more than 50 – 60.
As doctors, we most likely fall into the first category. We may be rich in the sense that our salaries are in the higher economic range, however, because of our expenses (houses, cars, student loan debt, private school tuition, practice overhead, etc.) and sometimes poor decisions, we have a tough time accumulating any real wealth. We’re also handicapped by the fact that we start along this financial journey relatively later in life.
Try going to our post: 20 Sites That Will Pay You to Read Books: Even though editing is not what this post is about, there are several companies that might do book editing such as Kirkus: I hope this helps and good luck on your book!
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.

Since 2008 I've helped hundreds of thousands of people get started with their own online business—and here's the common denominator: Everyone starts from zero. So, if you're feeling behind—don't worry. I'll catch you up quickly with what you need to know. Let's start with what this thing called "passive income" really means, and is it even possible?
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.

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Since David may never be coming back to this site, If anyone other than David can point me in the right direction, Id greatly appreciate it. I live in Chicago, and I need to buy a quality rental to hold long term somewhere but I have no idea where, and I really don’t want to buy in Chicago. Chicago is insanely corrupt and in HUGE debt. I cant leave Chicago in the near term, I take care of an aging parent, and if I left, my salary would drop by 50%. Id still like to diversify into a rental property.. but I feel that if I just call up a stranger, they’d attempt to sell me their best pig with lipstick, and pressure me to jump on the deal before someone else ‘stole’ it. I have no problem hiring a property inspector from a different city, but don’t want to waste hundreds of dollars if the agent is steering us towards crap property after crap property. I’m looking for broad advice. Any constructive reply appreciated. Thanks guys.
Residual income is the amount of net income generated in excess of the minimum rate of return. Residual income concepts have been used in a number of contexts, including as a measurement of internal corporate performance whereby a company's management team evaluates the return generated relative to the company's minimum required return. Alternatively, in personal finance, residual income is the level of income that an individual has after the deduction of all personal debts and expenses have been paid.