Investing in rental properties: Another form of real estate investment, rental investments (i.e. becoming a landlord) could steer you down the passive income path of steady monthly rent checks that you can use to pay off a mortgage loan on the rental property. After the mortgage is paid off, those monthly checks go right into your bank account -- potentially for years to come. 
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.
Building a smartphone or tablet app requires a fair amount of technical expertise, but it can pay off handsomely if successful. It doesn't have to be particularly complex or chock-full of features either; a simple one that solves a problem or is entertaining enough to attract users works fine. You never know what may suddenly become popular. For example, the minimalist game Flappy Bird was such a craze that at one point its developer was earning $50,000 dollars a day through in-app advertising. Of course, expecting a success like that is foolhardy, but one can always hope.
Author Bio: Sam started Financial Samurai in 2009 to help people achieve financial freedom sooner, rather than later. He spent 13 years working in investment banking, earned his MBA from UC Berkeley, and retired at age 34 in San Francisco. Everything Sam writes is based on first-hand experience because money is too important to be left up to pontification.

Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.