"But for our jobs, for how we make money, I think many of us — most of us — have one way we make money. It can be very risky. I've really come to believe, and have done a lot of research over the years, that one of the best ways that we can create real, legitimate professional stability for ourselves is by choosing to cultivate multiple income streams.
What I’m doing: My realistic goal is to have a blended annual return of 2x the risk free rate. With a current 5% hurdle, I am not paying down mortgages that cost less than 4%. Debt at 5% is a wash. My realistic blue sky scenario is a 3-4X rate of return over the risk free rate which can be achieved with property, stocks so far for the past five years, and certain private equity investments. Where I am dragging is my blended average CD interest rate of roughly 3% from an old CD coming due. I’ve rolled some money into a 12-month CD with CIT Bank at 2.5%. It’s the best rate I can find. 

Now, all that said, if capital (savings) grows faster than the growth of the economy, those with savings will see their wealth grow at a faster rate than those who rely on the growth of their income. While this is not an extension of Piketty's argument (you can't take an idea that applies to a population and a whole economy and boil it down to the individual like this), it's not an unreasonable conclusion to take and apply to your own life. (Piketty does talk about this on an individual level, but says it's more impactful for billionaires vs. millionaires – though we have limited data into individuals)

Has this thought ever struck you mind as what if your boss fired you overnight, what your course of action would be? I guess the answer is NOTHING! You have no monthly pay checks coming in, how are you going to put roof above your family’s head? How are you going to manage the bills payment? What would you feed to your family? An answer to all this lies in darkness…complete darkness in that situation. But I have answer to this question, because I am my own boss managing multiple things and earning from all of them at a time, losing one would not be that big deal to me.
The doctor or lawyer, for instance, could use her or his income to invest in a medical start-up or buy shares of medical companies he understands such as Johnson & Johnson. Over time, the nature of compounding, dollar cost averaging, and reinvesting dividends can result in her or his portfolio generating substantial passive income. The downside is that it can take decades to achieve enough to truly improve your standard of living. However, it is still the surest path to wealth based on the historical performance of business ownership and stocks.
A lot of people don’t even know about my life insurance business, but it’s a huge part of my success. Like my other big projects, however, I started it to help people. Over the years, I’ve seen so many people who are uninsured or underinsured. For whatever reason, they don’t understand the importance of life insurance. Worse, they don’t understand how affordable it is for the average family.

Most of us think of investment income as just the cash flow we get from bank interest, bonds, share dividends and property rents, some of which comes via a super pension.  But a more complete view is to also consider how growing the value of your investments can add to your spending potential.  This total return approach generates income from both income and growth to optimise spending from your portfolio across all market cycles, aligning cheap and expensive investments to your goals.