Rich people know the secret to wealth and peace of mind - and that is - having many cash-streams coming into their lives (and accounts!) instead of just one. One cash flow - say a salary or profit from a business - will not provide security in all times. On the other hand, multiple cash-flows provides stability and security. In case one cash-flow vanishes or reduces, the other one gives you comfort and sustenance.

2. Hobby income - Almost everyone has a hobby or an interest - art, cooking, fabrics, designing, books, photography, interest in History or coaching and training. The list is endless. You can use your hobby to generate income and cash-flow. I know many individuals who do this. There is a highly educated person I know who teaches on week-ends for joy and money. One man paints and sells paintings to sustain his art hobby. Another does historical tours. Indulge in your hobby and make it pay. Who knows, it may become your second career!
Whether you take a “distribution” (aka free-cash-flow) in the form of a dividend, interest payment, capital gain, maturing ladder of a CD, etc, you are still taking the same amount of cash out of your portfolio. Don’t fall for the trap of sub optimizing your overall portfolio’s performance because your chasing some unimportant trait called “income”.
Ebooks, which can be published through sites like Amazon Kindle Direct Publishing, are an increasingly popular option. Because these books are self-published, the process is quicker, allowing you to build residual income faster than the traditional publishing route. Whether it’s a romance novel or a how-to book on fly fishing, you can create a book and have it available for purchase in a matter of weeks.

Residual income is calculated as net income less a charge for the cost of capital. The charge is known as the equity charge and is calculated as the value of equity capital multiplied by the cost of equity or the required rate of return on equity. Given the opportunity cost of equity, a company can have positive net income but negative residual income.