Where we will be has an extremely high income tax (28-33%) that, once taken into account, won't leave us with enough money to live on if earning in the local currency (hence the plan for passive income in USD to subsidize it).

I began experimenting with entrepreneurial world about a two years ago and I have had a bit of experience in Muti-level Marketing, crypto-currencies, and most recently Ecommerce through a Ebay store. 

You also have to check on money currency conversions ratios and how income tax treaties are handled to get an idea of true returns.As you can see there are many,many layers to this.

Take your entire 80k and dump it into a forex trading account.

If you REALLY want to learn anything from A to Z, you have one currency: Your time.

For ex.. vacancy rates, rental income, expenses for the property, etc.

Not sure we'll ever see that in my lifetime unless there is some big-time currency crisis or a civil/world war.

Moreover the very same people does not make use of the interest tax reduction from their mortgage and paying way too much tax. how about the more riskier stockmarket, and the way more volatile commodities and Forex.

For ex, dont ask a contractor " hey , what should I do to make it legal "  .

Nobody can consistently time a market over the long term (stock market, real estate, options, crypto-currency, etc.).