What’s also really important to realize here is that when I took the exam I was teaching people to study for, I didn’t get a perfect score. In fact, I didn’t even get close to a perfect score. I passed. But I also knew a lot about this exam—way more than somebody who was just getting started diving into studying for it. And it was because of that, because I was just a few steps ahead of them, that they trusted me to help them with that information. To support this, I provided a lot of great free value to help them along the way. I engaged in conversations and interacted in comments sections and on forums. Most of all, I just really cared about those people, because I struggled big-time with that exam myself.
All wages and any other compensation for services performed in the United States are generally considered to be from sources in the United States. The place, where the personal services are performed, generally determines the source of the personal service income, regardless of where the contract was made, or the place of payment, or the residence of the payer.
This is an interesting take and good advice for those who probably do not need to ever worry about becoming destitute. I’m sorry but too many of your options including your own list of income require quite a bit of initial investment/capital and these suggestions are useless to those living paycheck to paycheck. I’d like to see the average low to middle income household purchase additional property for rental, invest in their portfolio (if they can even start one), or even afford to have a vehicle or room to rent. Far too first world of a solution for the general public.
No one wants to plan for a loss but it is always better to be prepared. US have recently seen a real estate meltdown that has caused the entire economies of the world to go into recession. So, it is very important to foresee such meltdowns and be prepared for losses. A second income source will ensure that you have enough rotational money to see you through losses.

To your point about Municipal Bonds, my concern is tax reform. While everything is mostly being worked behind closed doors (and likely wont ever see the light of day). There is still the chance they propose to limit the amount of the tax free nature of these bonds. While I dont sen panic in the streets, I do see a scenario where bond prices get additional pressure because municipalities have to increase rates due to people putting their money to work elsewhere.

“The biggest surprise is real estate being second to last on my Passive Income Ranking List because I’ve written that real estate is my favorite investment class to build wealth. Real estate doesn’t stack up well against the other passive income sources due to the lack of liquidity and constant maintenance of tenants and property. The returns can be huge due to rising rental income AND principal over time, much like dividend investing. If you are a “proactive passive income earner” like myself, then real estate is great.”
The Indian rupee (₹) is the only legal tender in India, and is also accepted as legal tender in neighbouring Nepal and Bhutan, both of which peg their currency to that of the Indian rupee. The rupee is divided into 100 paisas. The highest-denomination banknote is the ₹2,000 note; the lowest-denomination coin in circulation is the 50 paise coin.[319] Since 30 June 2011, all denominations below 50 paise have ceased to be legal currency.[320][321] India's monetary system is managed by the Reserve Bank of India (RBI), the country's central bank.[322] Established on 1 April 1935 and nationalised in 1949, the RBI serves as the nation's monetary authority, regulator and supervisor of the monetary system, banker to the government, custodian of foreign exchange reserves, and as an issuer of currency. It is governed by a central board of directors, headed by a governor who is appointed by the Government of India.[323] The benchmark interest rates are set by the Monetary Policy Committee.

The bottom line is, it’s smart to have multiple income streams no matter who you are. Why? Because the more ways you can earn money without compromising your integrity, the better off you’ll be. And if you’re self-employed, having multiple income streams is almost essential. Not only will you enjoy a higher income, but you won’t go broke if one stream ends out of the blue.
The reverse can also be expected unless the rents rise too.  This rental increase might occur if we imagine interest rates are rising because the economic environment is improving.  At present, it is widely expected that rates will rise ever so slowly over many years.  Indeed the US has been looking for the courage to do this over recent months and they may start rising there soon.