> People with high incomes living alone in multi bedroom units objectively should leave.

Who cares how high their income is or how big the property is? If they pay the rent and want to continue living there, they should be able to continue living there. Taking someone's home away from them because "now you earn more money" or "now you're less people" sounds very inhumane, and I'm glad Spain wouldn't allow such discrimination.

I don't know why you bring up US laws, utterly irrelevant in this submission.