The original version of Barbara Winter’s book, Making a Living Without a Job, came out in 1993, and in it, she recommended creating multiple "profit centers," as opposed to building a single income stream. Over ten years later,  Robert Allen, the real estate entrepreneur, also wrote a couple books promoting the idea of multiple streams of income. Back then, building more than one source of income was difficult, time-consuming, and expensive. Fortunately, things have changed today. The Internet has made it easier, faster, and more affordable to generate multiple income streams.
Another way to wring income out of stocks, even if they don't pay dividends, is to buy stocks that you expect will appreciate in value over time and then, when you need income, sell some shares. If you have a fat portfolio of such stocks when you retire, you might sell some shares every year to create a cash stream for yourself. Studying and choosing the stocks that will perform very well for you is easier said than done, though, so if you don't have the interest, skills, or time to become your own stock analyst, consider simply investing in a low-fee broad-market index fund or two, such as one based on the S&P 500. Here's how much you might accumulate over several periods if your investments average 8% average annual growth:

And real estate does more than just track inflation – it throws off income (which is important to some people and useful to most). And while your underlying asset is appreciating, the income also grows as rents increase over time. And if you make smart and well-timed purchases, both rents and asset values can increase at well above the rate of inflation.
This was a very inspirational article! I too spent 20+ years in a high-stress career selling a high-end product under a 100 percent commission plan; that is, no salary! I realized, after racking up millions of frequent flyer miles, that there had to be a better and less-stressful way of making a living. My goal was to design my own lifestyle free of corporate shackles, which required a pre-determined amount of passive income.
There are a ton of ways to diversify your investments, some of which can send real income your way. By opening a brokerage account and investing in ETFs or mutual funds, you can earn real returns you can use to supplement your income. Of course, the flip side can also happen – as in, you can lose money. So, make sure you understand the risks before you dive in.