​Self Publishing is mainstream today. When you purchase an eBook off of Amazon there’s a pretty good chance you’re buying a self-published book. Self-publishing is also ridiculously easy. I tried this a few years ago and couldn’t believe how simple the process was. To self-publish a book you’ll first need to write and edit it, create a cover, and then upload to a program such as Amazon’s Kindle Direct Publishing. Don’t expect instant success though. There will need to be a lot of upfront marketing before you can turn this into a passive income stream.
To these human costs can be added the massive economic waste associated with the water and sanitation deficit.… The costs associated with health spending, productivity losses and labour diversions … are greatest in some of the poorest countries. Sub-Saharan Africa loses about 5% of GDP, or some $28.4 billion annually, a figure that exceeds total aid flows and debt relief to the region in 2003.Source 10
The engineering industry of India includes its growing car, motorcycle and scooters industry, and productivity machinery such as tractors. India manufactured and assembled about 18 million passenger and utility vehicles in 2011, of which 2.3 million were exported.[179] India is the largest producer and the largest market for tractors, accounting for 29% of global tractor production in 2013.[179][180] India is the 12th-largest producer and 7th-largest consumer of machine tools.[179]

Add Leverage (Mortgage) and you greatly increase the ROI especially from the perspective of using Rents (other peoples money) to pay down the mortgage and increase your equity in the property over time. At this point then yes price appreciation is secondary bonus and we have an arguement of how and why Real Estate can be better than Growth Stocks in some scenarios and for some investors.
These days, low-risk bond yields aren’t enough to meet most income needs. When investing in bonds, the income typically comes as coupon payments – contractually guaranteed interest payments at predictable intervals.  There are many kinds of bond income available, so you must strike a balance between reaching for higher income (yield) and limiting risk.