P.S. I also fail to understand your fascination with real estate. Granted we’ve had some impressive spikes along the way, especially with once in a life time bubble we just went through. But over the long term (see Case Shiller real estate chart for last 100 years ) real estate tends to just track inflation. Why would you sacrifice stock market returns for a vehicle that historically hasn’t shown a real return?
The previous blog post in this series noted that income (measured by labor market earnings) appeared to be 33 percent more persistent than wealth. In their Regional Economist article, Gayle and Hincapié also noted that “using one number to summarize the intergenerational persistence of earnings and wealth cannot answer whether such persistence is due to the inability of the poor to escape poverty or the persistence of wealth and income at the top.”
4. Calculate how much passive income you need. It's important to have a passive-income goal — otherwise, it's very easy to lose motivation. A good goal is to try to generate enough passive income to cover basic living expenses such as food, shelter, transportation, and clothing. If your annual expense number is $30,000, divide that figure by your expected rate of return to see how much capital you need to save. Unfortunately, you've got to then multiply the capital amount by 1.25 to 1.5 to account for taxes.
There are three main categories of income: active income, passive income and portfolio income. Passive income has been a relatively loosely used term in recent years. Colloquially, it’s been used to define money being earned regularly with little or no effort on the part of the person receiving it. Popular types of passive income include real estate, peer-to-peer (P2P) lending and dividend stocks. Proponents of earning passive income tend to be boosters of a work-from-home and be-your-own-boss professional lifestyle. The type of earnings people usually associate with this are gains on stocks, interest, retirement pay, lottery winnings, online work and capital gains. 

Establishing residual income allows you to accumulate wealth faster, have a more flexible lifestyle and maintain a diverse financial portfolio. As with any successful investment, hard work is required. With residual income, however, that work tends to be upfront. Once your revenue stream is established, the work and time involved is significantly lower than active income sources. With residual income, you’ll secure funds for your future, have a better idea of where you stand financially and enjoy peace of mind knowing you’re maintaining lucrative, long-term investments.  
The U.S. Internal Revenue Service categorizes income into three broad types, active income, passive income, and portfolio income.[1] It defines passive income as only coming from two sources: rental activity or "trade or business activities in which you do not materially participate."[2][3] Other financial and government institutions also recognize it as an income obtained as a result of capital growth or in relation to negative gearing. Passive income is usually taxable.
Department C has earned $142.5 million residual income as compared to $40 million earned by department P. Residual income allows us to compare the dollar amount of residual income earned by different departments. Since the residual income in both cases is positive, we conclude that both have met the minimum return requirements. However, with residual income is not easy to compare performance.
Writing an e-book is very popular among bloggers, as many have noted that “it's just a bunch of blog posts put together!” You will not only have to make an investment of time and energy to create the e-book, but market it correctly. However, if marketed correctly (through blogging affiliates in your niche, for example), you could have residual sales that last a very long time.
One word of advice, and something I intend to do once I have the money saved up, is to build or buy out property that can support apartments or townhomes. One tough mistake some people make is buying a pair of homes to rent out and they get a nice $2,000-$3,000 a month but that’s it. Buying a house is expensive and the rental prices keep lower income families from potentially coming to you with their money to rent. If you have an acre to work with (more or less is OK too) you should be talking to a contractor to build apartments or townhomes. You will make a little less per unit BUT your audience grows significantly because now you can have college students, single parents, older folks, etc. all able to afford your rental units AND instead of capturing one $1,000-$1,500 a month payments, you can probably charge $700 a month per unit (or more, depending on the market) and build maybe 3, 4, 5, 10 units for the price of a home or two and now you’re making something like $2,100-$10,000 a month. It all depends on what you have to invest but if you’ve got $250,000+ I’d highly suggest you talk to a bank/investor that can get you in touch with a good contractor to build on a property and get permits and take out a matching $250,000 loan (I’ve read that $500,000 is plenty to build a good amount of apartments to start) and you can fill up your apartments and make a killing every month. You’ll have more tenants to deal with but if you’re competitive with your pricing you won’t have a hard time keeping tenants or replacing them.