The theoretical generalization to more than one period is a multi-period wealth and income constraint. For example, the same person can gain more productive skills or acquire more productive income-earning assets to earn a higher income. In the multi-period case, something might also happen to the economy beyond the control of the individual to reduce (or increase) the flow of income. Changing measured income and its relation to consumption over time might be modeled accordingly, such as in the permanent income hypothesis.
Think about it.  If you are saving for retirement, you are trying to save enough in investing to generate enough income to replace your primary salary.  Let’s take my friend’s example above: $50,000 a year.  To generate $50,000, you would need to have almost $1,700,000 saved, and be able to generate a 3% cash flow on that money (which is reasonable if invested in dividend paying stocks).
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?
My favorite type of semi-passive income was rental property because it was a tangible asset that provided reliable income. As I grew older, my interest in rental property waned because I no longer had the patience and time to deal with maintenance issues and tenants. Online real estate became more attractive, along with tax-free municipal-bond income once rates started to rise.
India's reliance on external assistance and concessional debt has decreased since liberalisation of the economy, and the debt service ratio decreased from 35.3% in 1990–91 to 4.4% in 2008–09.[293] In India, external commercial borrowings (ECBs), or commercial loans from non-resident lenders, are being permitted by the government for providing an additional source of funds to Indian corporates. The Ministry of Finance monitors and regulates them through ECB policy guidelines issued by the Reserve Bank of India (RBI) under the Foreign Exchange Management Act of 1999.[294] India's foreign exchange reserves have steadily risen from $5.8 billion in March 1991 to $426 billion in April 2018.[295] In 2012, the United Kingdom announced an end to all financial aid to India, citing the growth and robustness of Indian economy.[296][297]

These numbers seem counterintuitive for most of us in the financial advice industry. Do we not expect our contribution to the investor’s welfare to be proportionately larger than what these numbers show? Is the median annual income from financial capital really this small? Will this pattern — representing the prior generation — hold true of the baby boomers?
What I Do: I’ve set up multiple investment accounts outside my main operations bank that deals with working capital e.g checking, paying bills. By transferring my money to a couple brokerage accounts and two other banks as soon as it hits my main bank I no longer have temptation to spend on frivolous things. As a result, I can wake up 10 years later and reap the rewards of compounding. My 401(k) is the best example where constant contributions over 18 years has grown to over $500,000 without any savings pain given it just became a part of life. Real estate is also a fantastic asset class for the long term. It’s fantastic to enjoy your home, pay down your mortgage each month, and end up with a paid off asset that has likely appreciated during your time of ownership. 
Blogging is a great way to stream in income. Some consider blogging as a passive income source and they are pretty much dead wrong. It takes a lot of hard work and time to build your blog into a viable business.  It is not a good get rich quick scheme, but with time and patience you can easily earn a full time income and even exceed what you make at your full time job if you are really good.

Quick story: Remember that $1.18 I found in the couch? Even when that increased to $30 to $50 a day, it still wasn’t enough to live on. So I looked for other options. In August 2008, after people started to know who I was and how I could help them pass the LEED certification exam through my blog, I wrote an ebook. It included all the information I knew about passing this exam, and I sold it on my blog for $19.95.

Purchasing a rental property is another common way that individual generate an income stream.  It is very similar to investing, in that you take a sum of money to purchase the property, and the property returns a cash flow – rent.  You do have expenses related to this that are different from investing, such as a mortgage, utilities, property taxes, etc, which all must be taken into consideration when calculating a return on rental property.

Real estate crowdsourcing allows you to surgically invest as little as $5,000 into a residential or commercial real estate project for potentially 8 – 15% annual returns based off historical data. Such returns are much better than the average private equity, CD, bond market, P2P lending, and dividend investing returns. With P2P lending, borrowers can sometimes default and leave you with nothing. At least with real estate crowdsource investing, there’s a physical asset that’s backing your investment.
The doctor or lawyer, for instance, could use her or his income to invest in a medical start-up or buy shares of medical companies he understands such as Johnson & Johnson. Over time, the nature of compounding, dollar cost averaging, and reinvesting dividends can result in her or his portfolio generating substantial passive income. The downside is that it can take decades to achieve enough to truly improve your standard of living. However, it is still the surest path to wealth based on the historical performance of business ownership and stocks.
The obvious way to earn a second income is to get a part-time job. If you are not currently working, this is an excellent way to start as it gives you the freedom and flexibility to start other passive income opportunities.  The other option is to simply work from home full time which frees up commute time so you can focus on building more income streams.
"Full income" refers to the accumulation of both the monetary and the non-monetary consumption-ability of any given entity, such as a person or a household. According to what the economist Nicholas Barr describes as the "classical definition of income" (the 1938 Haig-Simons definition): "income may be defined as the... sum of (1) the market value of rights exercised in consumption and (2) the change in the value of the store of property rights..." Since the consumption potential of non-monetary goods, such as leisure, cannot be measured, monetary income may be thought of as a proxy for full income.[3] As such, however, it is criticized[by whom?] for being unreliable, i.e. failing to accurately reflect affluence (and thus the consumption opportunities) of any given agent. It omits the utility a person may derive from non-monetary income and, on a macroeconomic level, fails to accurately chart social welfare. According to Barr, "in practice money income as a proportion of total income varies widely and unsystematically. Non-observability of full-income prevent a complete characterization of the individual opportunity set, forcing us to use the unreliable yardstick of money income.
3) Create A Plan. Mark Spitz once said, “If you fail to prepare, you’re prepared to fail.” You must create a system where you are saving X amount of money every month, investing Y amount every month, and working on Z project until completion. Things will be slow going at first, but once you save a little bit of money you will start to build momentum. Eventually you will find synergies between your work, your hobbies, and your skills which will translate into viable income streams.
While compiling this list, I did my best to avoid scams, and stick with practical ideas that work. I have tried many (but not all) of these ideas. Some of these helped me earned a few dollars here and there, but there are some that helped me earn extra money on the side every single day — and some are still providing me with revenue! Note that not all ideas will fit your skills and abilities. What works for you depends on your abilities and your current financial situation.
Most earners__ salaried or businessmen__work hard to earn money for the family and the self. However, not all of these people, after they have earned money, also make their money work hard to generate some extra income. There are quite a few options which people could use to earn some extra income. Two of those routes are putting a small part of your hard earned money into Liquid Funds and/or accrual funds. Investing in these funds could also help retired people to earn some extra income. And if they are already getting pension, earnings from these funds could work as a source for a second income for them.
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.
As a private lender, you can lend to anyone in your social circle. For example, many home rehabbers need access to a source of capital they can tap into very quickly in order to fund the initial purchase of their properties. You can partner with a rehabber who uses your capital for a short-term in exchange for an interest rate that is mutually agreed upon.
Income from the performance of services directly related to the use of a vessel or aircraft is treated as derived entirely from sources in the United States if the use begins and ends in the United States. This income is subject to nonresident alien withholding if it is not effectively connected with a U.S. trade or business. If the use of a vessel or aircraft either begins or ends in the United States, refer to Transportation Income in Publication 515, Withholding of Tax on Nonresident Aliens and Foreign Entities.
Making legitimate passive income isn’t as difficult as you might think. Some of the best passive income ideas might take a little time to set up but can start cash flowing within a couple of months and will provide a consistent monthly income for years or more. The most important point is just to get started. You make exactly $0 on the passive income sources you never start.
Note: A Tax Bulletin is an informational document designed to provide general guidance in simplified language on a topic of interest to taxpayers. It is accurate as of the date issued. However, taxpayers should be aware that subsequent changes in the Tax Law or its interpretation may affect the accuracy of a Tax Bulletin. The information provided in this document does not cover every situation and is not intended to replace the law or change its meaning.
As the third-largest economy in the world in PPP terms, India has attracted foreign direct investment (FDI).[301] During the year 2011, FDI inflow into India stood at $36.5 billion, 51.1% higher than the 2010 figure of $24.15 billion. India has strengths in telecommunication, information technology and other significant areas such as auto components, chemicals, apparels, pharmaceuticals, and jewellery. Despite a surge in foreign investments, rigid FDI policies[302] were a significant hindrance. Over time, India has adopted a number of FDI reforms.[301] India has a large pool of skilled managerial and technical expertise. The size of the middle-class population stands at 300 million and represents a growing consumer market.[303]

If you want to top up your income without taking on a strenuous second job, your first port of call should be your very own skillset. If you have a natural talent that could help others, you have an instant “in” to easy money. Whether you’re a gifted guitarist, mathematical genius or speak a second language, almost any talent can be turned into cash. Offering one-to-one coaching is a flexible way to make a solid hourly rate, and enables you to take on as much or as little work as you wish. Find local clients by placing adverts in the library, schools and community bulletin boards and share your talent in exchange for a fee.
In addition to opening a brokerage account, you can also invest in peer-to-peer lending firms like Lending Club. I’ve been using Lending Club for a few years, and my net annualized return was 6.02% percent last year. Picking the right investments is easy since the platform offers automatic investing, but you can also pick your own notes if you're brave and want to learn the best ways to leverage the Lending Club platform.