Now, all that said, if capital (savings) grows faster than the growth of the economy, those with savings will see their wealth grow at a faster rate than those who rely on the growth of their income. While this is not an extension of Piketty's argument (you can't take an idea that applies to a population and a whole economy and boil it down to the individual like this), it's not an unreasonable conclusion to take and apply to your own life. (Piketty does talk about this on an individual level, but says it's more impactful for billionaires vs. millionaires – though we have limited data into individuals)

The World Travel & Tourism Council calculated that tourism generated ₹15.24 lakh crore (US$210 billion) or 9.4% of the nation's GDP in 2017 and supported 41.622 million jobs, 8% of its total employment. The sector is predicted to grow at an annual rate of 6.9% to ₹32.05 lakh crore (US$450 billion) by 2028 (9.9% of GDP).[250] Over 10 million foreign tourists arrived in India in 2017 compared to 8.89 million in 2016, recording a growth of 15.6%.[251] India earned $21.07 billion in foreign exchange from tourism receipts in 2015.[252] International tourism to India has seen a steady growth from 2.37 million arrivals in 1997 to 8.03 million arrivals in 2015. The United States is the largest source of international tourists to India, while European Union nations and Japan are other major sources of international tourists.[253][254] Less than 10% of international tourists visit the Taj Mahal, with the majority visiting other cultural, thematic and holiday circuits.[255] Over 12 million Indian citizens take international trips each year for tourism, while domestic tourism within India adds about 740 million Indian travellers.[253]

4. Save, build and run a bread-n-breakfast place. Look at airbnb Vacation Rentals, Homes, Apartments & Rooms for Rent - Airbnb for inspiration. My wife runs one (Firdaus, Naukuchiatal) , it is not an income as of now but if you are on it for enough time, it would be, when you grow old. It doesn't have to be a fancy and glamorous thing. It could be a  2 nice-n-clean room in a city where you live. If you have a big house, it could be a  part of your house.
According to Uncle Sam, you need to be "materially involved" in an enterprise to earn active income. With passive income, it's just the opposite, as the IRS deems you to be earning passive income if you're not materially involved with a profit-making enterprise. By and large, expect income to be taxable if you are engaged in a passive income enterprise. You will need to report earnings to the IRS.
Those who choose to focus on passive income will need either family money, funds from investors, or the nerve to borrow large sums by taking on debt to fund the purchase of assets. The easiest to understand is someone who takes out substantial bank loans to build an apartment building or buy rental houses. Although this can turn a very small amount of equity into a large cash flow stream, it is not without risk. When using borrowed money, the margin of safety is much smaller because you can’t absorb the same degree of setback before defaulting and finding your balance sheet obliterated.
"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.
For a person working for a wage, their source of income is their job, or their labor (aka their time that they sell to someone). But you can own a house, and rent it out, and when your renters pay you renter every month, the source of that income check is your rental property, or your house. It would just be called rental income. If you have money in the bank in an account that pays interest, those interest payments are another source of income. We can say the source is interest payments, or we can identify the asset that is generating rent, and say your money in the bank that is generating “rent” (aka interest) is your source of income.