A good rule of thumb is whether the vehicle TOWED outweighs the TOW VEHICLE. If so, you should have brakes on the TOWED vehicle also. And, if your camper supports tow brakes and you want them used, you can tell the renter they need that capability. I've lost a few renters this way, but so far the camper keeps coming home safe.
My brother tried to rent a trailer and tow it with a V6 SUV with no brake controller. I talked him into renting a 3/4 ton pickup instead. He was so thankful that I talked to him first. After his trip to Yellowstone, he said he would have never made it safely with his SUV. Worse case would be an accident, or damage to the renters truck/suv. I asked my brother if he was ready to replace his transmission near Yellowstone if the overload destroyed it. After thinking about that scenario, he decided on renting the truck.
I have this on standby and plan on charging $30 add on to the rental. It is blue tooth and connects between trailer plug and vehicle. If the tow vehicle is within its capability for the trailer, this is any easy way not to miss out on revenue. I know of a lot of F150’s without brake controllers