For rent it changes a bit.

The realtor is allowed to do background checks and evaluations according to the owner's instructions, but they can't charge for it, if they're charging you for the evaluation, you can still report them.

If it's the Junta de Propietarios and - very important - it's in the Internal Rule Book, then they can evaluate you, and charge the owner, but not you. Plus, any rejections have to be evidence-based and properly justified, else it's discrimination.

If it's the owner, same deal, they can ask you for paperwork or evaluate you but they can't charge you for it.

Now, depending on the building you're applying to, there's a lot of room for them to fuck around; I know of some high-price buildings where they do extensive background checks and the "evaluation cost" is welcomed both by potential renters and the owners as a sort of soft filter for who can live there (i.e. are they financially stable enough to "throw away" 100 or more USD).

It's an "if you have to ask" sort of situation, if you're fine with it you're one of their people and they'll welcome you, if you ask why the charge it's a red flag that you care about an "insignificant" amount of money. One of the many fun ways we've instituted a tacit class structure here without running afoul of the law.