Estimated GDP per capita of India and United Kingdom during 1700–1950 in 1990 US$ according to Maddison. However, Maddison's estimates for 18th-century India have been criticized as gross underestimates, Bairoch estimates India had a higher GDP per capita in the 18th century, and Parthasarathi's findings show higher real wages in 18th-century Bengal and Mysore. But there is consensus that India's per capita GDP and income stagnated during the colonial era, starting in the late 18th century.
Book sales ($36,000 a year): Sales of How to Engineer Your Layoff" continue to be steady. I expect book sales to rise once the economy starts to soften and people get more nervous about their jobs. It's always best to be ahead of the curve when it comes to a layoff by negotiating first. Further, if you are planning to quit your job, then there is no downside in trying to engineer your layoff so you can get WARN Act pay for several months, a severance check, deferred compensation, and healthcare.
One of the things I'm surprised your article doesn't mention is the tax advantages of this type of investment. The depreciation and rehab costs (purchasing distressed properties) can be huge deductions to ones income taxes, which none of the others have. Then, along with the appreciation of real estate, this passive income investment outperforms the notion of maxing out my 401k as well.
In focusing on your wealth management goals, investment income is obviously critical but you might fund your goals from wider sources of income. A typical long-term portfolio might produce about half its return as income and the other half as capital growth, though in times of duress the capital growth component wanes. In this low-interest rate climate, some sources of income have become quite expensive and may prove disappointing against your spending needs. But by tax efficiently and sustainably drawing income from wider sources, you might meet your goals while more prudently balancing risk against reward.