If you happen to own a home, apartment, or office space, you have a great source for generating passive income at your fingertips. Peer-to-peer property rental site Airbnb has made it extremely easy for real estate owners to make extra money by renting out their homes to guests for short durations. If you're uncomfortable with such a model, you can also use sites like NestAway to find tenants for your property without having to deal with brokers.

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.