Pray tell, what kind of low stress job lets you earn $500k/year with 20 hours/week? (Actual job, please, not "4-hour workweek" style passive investment income.)
There are many such jobs available. We discuss this in detail at my weekend seminars, which you may attend for the low low price of $20k.
Seriously though, I think I might know of some semi-retired lawyers who make that sort of money, but that only happens after a lifetime of option #1.
Edit: you could make this kind of money with very little work as a board member of a large corporation. Once again, see option #1 for how to get to that point in your life.
They were all owners of lifestyle businesses that had been running for a while. They either hired a full time manager to manage the business, or everything basically ran on autopilot and required less attention.
Some of them got their by working their butt off, some got there by inheriting the business and never really having to work all that hard.