I think many people are imagining it wrong, though ... it's not like every house in Barcelona has a parking garage, especially in the old town, but also in newer dense neighborhoods. It's just my estimate based on observation but I would say apartment buildings WITH a parking garage are the exception rather than the norm. If they have a garage, you still have to pay extra for the spot usually.

As a resident you can apply for resident street parking, which gives you preferential parking in the parking zones associated with your neighborhood. That's not free, either, but you can park at a discount.

But typically renting an apartment doesn't come with any guarantee that you'll have guaranteed immediate access to parking close to your place ... heck, if you're living in the old town you might have trouble finding a place to put your bicycle ....

EDIT: the article only mentions selling, not renting, so, not sure how that compares really ...