Cost of test drives for the dealer

Hello together, first hello (my first post) and at the same time sorry, if it has landed in the wrong forum. Please postpone if necessary. It’s about the following: I have a small idea about cars and would need to have access to cars at a dealer. Logically, the dealer will not simply pull out his cars (even if he is convinced of my idea), in return I will advertise his car house. Therefore, the question arises to me, which fare n for a dealer on a test drive of a maximum of one hour (apart from fuel costs, which I would of course bear)? Are there possibly people here who work in a car dealership and know what could speak against it from the dealer’s point of view? Thank you all! BlackWolf