I do also have a GREAT and almost FREE health care here. In Spain $1-$2 million would probably be the equivalent of that $5million for US. Again, depends on many factors.
And yes, one could go with a lower figure if he already has a home, retirement pension, additional income, less years to live, very frugal lifestyle, etc etc...
But the geographical factor is *EXTREMELY* important.
Fortunately I plan to always live here. Not just because of "cost of living" but QUALITY of living... and WEATHER! *Most* of the world (including many parts of my damn country!) is too fucking cold for my taste.
Now you mentioned Spain, I was actually considering of buying 2 x 500k€ flats in Barcelona and AirBnb the fuck out of them.
Work while having a vacation. Sound like a brilliant idea.
Not the best of the ideas. Touristic apartments are having a regulation tightening specially in Barcelona. Risky business I would say. You might be earning like a boss this year and the next one be out of the market because of some regulation that forbids you to rent it. In fact that is ALREADY happening.
Also Barcelona (and Madrid) and among the most expensive cities to live in Spain. Higher salaries yeah, but if you are not gonna work there you will just "enjoy" the higher cost of living. Still, WAY lower than US, of course.
About renting... currently the best investment are more "modest" 2-3 room apartments valued from 50 (reform usually needed) to 250K (more premium zones) € that you can rent for 5-10% that. Long term, so hassle free.
Or lousy apartments with many rooms near universities that you can rent to students.
It's a job in itself to take care of your "business" and properties but it's a reasonably safe investment with a good return if you know what you are doing.