It can be written as one word: “rentalwise”. You won’t find it in a dictionary. You can add the suffix “-wise” to any noun. You won’t get a real word, but you can use it informally. My mom used to say “that’s the way it crumbles, cookiewise”, instead of “that’s the way the cookie crumbles”. “-wise” means “in the way of”. So “rentalwise” means “in the way of” or “as pertains to” rentals.