I'm a non-resident seeking to buy real estate. Santander refused, stating at least precaria would be needed (in line with what barbablanca wrote above) and they can't open a bank account for a non-resident.
Galicia accepted me, based on DNI and Passport. They also asked a few of the typical KYC questions (income and wealth situation and if I will be able to provide documentation on that, haven't been asked to provide any specific documents yet though).
Now awaiting the account details, then the interesting part will be if I can really just wire and withdraw USD that easy. I would be positively surprised if it works.