Any insights on living in (retiring to) a place like Spain?

Ok, I’m still several years away, but close enough to be pondering the form my retirement will take.

I have heard stories of people who happily retire to other countries to enjoy a lower cost of living and generally more relaxed lifestyle. It is my understanding that in some locals one can live like royalty on what would be considered a modest income here in the States.

Anyone out there have any practical advice to share on living in Spain?

What is the cost of living relative to the US?

What about things like basic medical service for foreign nationals?

Any barriers to citizens of other countries owning property, living there indefinitely, etc….?