Interesting hearing the situation in Spain! In the US, you sometimes see arguments centered around there being lots of vacant housing, but they usually neglect to mention that a significant majority of those units are actually either (a) so rundown they're actually uninhabitable, (b) empty for a month or two between when the old tenants leave and the new tenants move in, or (c) in middle-of-nowhere cities/towns that don't have any jobs.