“I’m thinking about buying a condo that was built in the 1960s. It’s fine right now, but what happens in, say, another 50 years? If it has to undergo major renovations or be rebuilt entirely, who pays for that?”
It’s not likely that a condo complex or even individual buildings will need to be rebuilt entirely.
Regarding major renovations, most homeowner’s associations will budget for that work and do it as needed. Only an unusually poorly run HOA would let work build up until it all needs to be done at once and there’s no money to do it.
As a side note, the average time that someone owns a San Diego condo is about 7 years, so it’s unlikely you’ll own it for 50 years.
…If the majority of people start holding their real estate that long, I’d need to find another profession!