mu uncle has a 3 bay car wash and 6 vaccums and 1 air freashner machine. He has 1 drink machine, and 6 little vending machine for armour-all, towels, etc. He does pretty well.
IMO I would do atleast 1 touchless car wash. Because you will always have plenty of people out there esp in the winter that don't want to wash there car and will pay 5-7 bucks to get it washed.
*** this is very important if he can afford it tell him to get a water heater. My uncle looked at one and it was around 1,000-2,000 bucks. People avtuall notice that. It does a awesome job in the automatic car wash. If my car is not really dirty I can go to my uncles car wash that does not have hot water and spray my car off and it will still be dirty, but if i go down the road and use the hot car wash ( self service bay) I can spray the car off and it will look way better.