It covers Rental Income (Real Estate) or Interest Income (Bank Deposits). Though it is best suited for retirement planning but it can also act as second income during working years. Big question is how to fix the target for Second Income. Very simple, if your Monthly Expense is 50k & residential property can yield rent of 25k then you need 3 residential units i.e. one for self and two for second income source.
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”.
Don't mistake passive income with zero work. It's still work, it's just that your income is not directly tied to the hours worked. Anyone who owns rental properties knows that it's considered passive income but there is quite a bit of work involved. The work is front heavy but if you are lucky, you can collect rental checks without incident for many months before having to do work.

I agree that it is important to establish multiple sources of income, but I would be hesitant to group dividend stocks and real estate into the “multiple streams” bucket. Those are investments, and living off of investment income because you are in an emergency state is not a good plan. Cash flow from investments ebbs and flows more than the cash flow from a day job.
Passive income is defined by Wikipedia as “income resulting from cash flow received on a regular basis, requiring minimal to no effort by the recipient to maintain it”. And while the ‘no effort’ part of the definition is very enticing, the truth is that generating passive income requires a massive amount of effort. And this effort needs to be exerted up front and then sustained for months, and maybe even years, until your venture starts returning profits. And even then, you'll have to monitor your income streams to make sure it’s all going smoothly. It's certainly not an easy endeavour, no matter what most people may tell you, and it requires an investment of something far more valuable than money: time. But if you are up for it, then here are 14 ideas that you can use to start earning passive income.
Ethiopia’s main challenges are sustaining its positive economic growth and accelerating poverty reduction, which both require significant progress in job creation as well as improved governance. The government is devoting a high share of its budget to pro-poor programs and investments. Large scale donor support will continue to provide a vital contribution in the near-term to finance the cost of pro-poor programs.
For economic growth and almost all of the other indicators, the last 20 years [of the current form of globalization, from 1980 - 2000] have shown a very clear decline in progress as compared with the previous two decades [1960 - 1980]. For each indicator, countries were divided into five roughly equal groups, according to what level the countries had achieved by the start of the period (1960 or 1980). Among the findings:

There was a time when CDs would produce a respectable 4%+ yield. Nowadays, you’ll be lucky to find a 5-7 year CD that provides anything above 2.5% The great thing about CDs is that there are no income or net worth minimums to invest, unlike many alternative investments, which require investors to be accredited. Anybody can go to their local bank and open up a CD of their desired duration. Furthermore, a CD is FDIC insured for up to $250,000 per individual, and $500,000 per joint account.

As an struggling young Engineer (back in the Carter era) I bought anything I could renovate then rent to justify paying the 18% interest. I never took vacations but worked on my properties all in the pursuit of passive income. I drove junk for many years & many months I just got by on credit cards. My friends & colleagues were amused by my ‘stupidity’ but most are still working to make enough for retirement.
I guess the people who bash this book would prefer to read a financial book by someone like Jane Bryant Quinn. How many people have made a fortune or any money at all following her advice? I rest my case.Or perhaps these bashers think the Road to Wealth is a college degree and work 9-5, 40 hours per week for 40 years and think that their employer will take real good care of them right? WRONG! Or perhaps these bashers feel the real key to wealth is to invest your 401 (k) money in your companies stock or you rate your wealth by your stock options huh? Ask employees invested in Lucent, Compaq or Enron how good they feel about retirement considering whats "left" in their company 401 (k) plan or by the value of their stock options (those who haven't been downsized that is).Robert Allens book is a excellent book for anyone who wants to reach permanent and rapid wealth. He teaches you how to invest with index funds and create cash flow with covered calls and options.He shows you how to 86 your job and start your own business through Network Marketing. He talks about the internet and licensing; real estate, discount mortgages and tax lien cerficates and then he shows you how to put it all together.Whats not to like about this book?I also recommend Who Stole the American Dream.For those who are happy with mediocity, keep your J-O-B *Which stands for just over broke) and read Jane Bryant Quinns book.
What I’m doing: I use this site to write out goals like 1) Generating $200,000 a year working 4 hours a day or less, 2) Trying to make winning investments, and 3) Keeping track of my passive income streams with free financial tools. My site and the community helps keep me accountable for progress. It’s important I do what I say, otherwise, what the hell is the point? You should consider starting a site or at least a private journal. Write out your specific goals, tell several close friends and stick to the plan.
Venture Debt – I invested $120,000 in my business school friend’s venture debt fund. He started his own after spending 8 years at one of the largest venture debt funds as a Managing Partner. I’m very focused on income generating assets in this low interest rate environment. The true returns are yet to be seen, as the fund has a 5-7 year life before it returns all its capital.
Thirst for income is likely to continue with interest rates expected to stay low, keeping government bond yields low for longer and their valuations unattractive.  Looking past bonds, the prices of high-dividend shares are historically high, which limits the likelihood that their dividends will rise markedly from here.  Striving too high for an income target tends to push your portfolio further out on the risk spectrum.