The 4% rule always sounded too aggressive for me but yeah, there are spots around the globe where you could theoretically take your $600k and peace out to an early retirement, leading a pretty basic lifestyle (check the list). Source: about 1 year ago

Have you had a look at https://nomadlist.com/fire yet? Source: over 1 year ago

Someone else posted this one, and there are probably other cost of living "calculators" out there where you can input income and find places you can afford to live. Source: over 1 year ago

The Nomad list has a FIRE calculator that used to be free and would list a bunch of cities all over the world and when/how much you would need to FIRE there based on your numbers. You need to sign up and pay a one time $90 fee now to access everything (I think like the top 10 places you could FIRE at this very moment/soonest) for free still though. It was really fun to play around and fantasize about retiring of I... Source: over 1 year ago

NomadList has a page on this: https://nomadlist.com/fire. Source: over 1 year ago

Selling software applications that solve actual problems of businesses = yes, check out https://postmake.io/open https://www.indiehackers.com/. Source: almost 2 years ago