I did the Korean thing for a year or so. ESL in Korea or Japan can be a good option if you're in your 20s and have an impractical BA (mine was in painting) and want to pay off loans fast. COL expenses are low. ESL as a field is pretty dead-end however unless you get an MA. In China, I tutor business clients on evenings/weekends to gain more insights about the culture, and it's a nice extra income, but I never liked doing ESL full-time.
At the moment I teach at an international school in Beijing, and salaries (and benefits for overseas hires) are easily triple what English language teaching pays. Also, you can find work virtually anywhere in the world vs. just the ESL markets (which are limited [edited to add: limited for Americans] mostly to Asia [for reasonable pay/savings potential] and South America).
Long-term visas for Europe can be a problem for Americans -- and Europe isn't a place to earn good money/save, but can be a good place to retire. Here's how one American family is going about their visa application for Spain, using their online income
http://life.almostfearless.com/want-to-move-to-europe-whats-an-american-to-do/Our history is patchwork:
I'm an American married to a Brit. We've lived a peripatetic life together in Asia and Australia (I lived/worked/studied in Europe before we met) for a decade. We've really enjoyed it but haven't saved as we should have.
We'll move to the UK next year to be closer to my MIL whose health is failing. We plan to live there for 6 years and I'll become naturalized (British passport) which will make retiring in Europe much easier. While in the UK, I'll do a (free, salaried) teaching cert in Design & Tech to increase my employment options at int'l schools when we return to Asia - a big money-saver esp if we have/adopt a kid. Also perhaps an MSc for various reasons. During our time there, we plan to buy a multifamily property in his hometown - which gets some of the highest rental returns in the UK, and pay cash for a handful of small, affordable flats/houses in the Mediterranean region for investment and potential retirement locations for us.
We're looking at Singapore or Taiwan for the next phase of our working lives, either directly after leaving the UK or after a sabbatical, working there for a number of years until FIRE.
Since home isn't just one place for us, we're looking at a balance of currencies and lifestyle options for our future.