When I was a working stiff, I lived in a whole bunch of big cities. Including Boston, Chicago, San Francisco, London, Paris, Barcelona, Helsinki, Singapore. They're lovely cities, but massively expensive, especially if you don't have a nice 9-5 career-type job. So I'm kinda surprised where I've ended up...
Argentina has a major currency problem, but that's an opportunity if you have passive (or remote) income in dollars or euros (especially if you bring cash money and change on black market). Our (former, although we still visit occasionally) apartment is in downtown Buenos Aires, within easy walking distance of many important colonial buildings, a lovely park, and a large riverside nature reserve. It's very civilized place, with great food and drink, and by far one the cheapest options (with the above proviso) for living in a major capital city. But property is priced in dollars, so while it's cheap to live, it's not cheap to buy (although it's pretty affordable compared with many capitals).
Instead, we're in a downtown apartment in Plovdiv, Bulgaria's second city (population less than 400k). This is a former European Capital of Culture, and it's a wonderful small city, full of ancient monuments. This morning, I walked 6km along newly paved walking/cycling paths, out past the Regatta Lake where the flocks of daybreak birds flew over me. The Regatta is an international rowing centre, but it also has a stadium, lots of tennis courts, football and basketball courts, outdoor gym. And a refurbished 25m pool (with an Olympic 50m competition pool in construction). Other mornings, I go the other direction, along a 2,000 years old Roman aqueduct and then up a quaint cobbled path to the top of Youth Hill. My swimming pass is 22 euros for 8 entries... and my walks are free. :-)
The name Bulgaria makes most folks think of unwelcoming Eastern Europe, and mobs of "Russian Mafia" roaming the streets in their blacked-out Mercs. And it's definitely not on any list of the world's best retirement destinations! But I've found that "it's tip-top, Tommy". :-) I've managed over 5 years here (now a Permanent Resident), which is the longest in one place since I was kid. It is safe, civilized, and the lucky recipient of oodles of EU funds which have upgraded parks, paths, roads and all kinds of local infrastructure and services (and not just the bank accounts of local Mafiosi).
Not only does Bulgaria have relatively low property costs, but it has very low living costs (including property "holding" costs). And it's not just cheap, it's a beautiful country. The Black Sea coast is great, and the Central Balkan National Park and the Pirin National Park are both spectacular. The weather is great, and so is the food. We don't stay in Plovdiv all the time: we have a country house just outside one of the National Parks (our neighbours are very warm and welcoming), and a holiday studio in Bansko (a charming little town and the largest ski resort). And there are cheap flights (Wizzair, EasyJet, Ryanair) from Sofia or Plovdiv, so we can easily (and inexpensively) pop over to UK, Spain, Cyprus, Turkey and elsewhere. We're lucky to enjoy a fantastic quality of life here, one we could only dream of in another country.