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.
Purchasing a rental property is another common way that individual generate an income stream.  It is very similar to investing, in that you take a sum of money to purchase the property, and the property returns a cash flow – rent.  You do have expenses related to this that are different from investing, such as a mortgage, utilities, property taxes, etc, which all must be taken into consideration when calculating a return on rental property.
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.
In focusing on your wealth management goals, investment income is obviously critical but you might fund your goals from wider sources of income.  A typical long-term portfolio might produce about half its return as income and the other half as capital growth, though in times of duress the capital growth component wanes.  In this low-interest rate climate, some sources of income have become quite expensive and may prove disappointing against your spending needs.  But by tax efficiently and sustainably drawing income from wider sources, you might meet your goals while more prudently balancing risk against reward.