If you are considering detailing - another service to consider is rust protection. There's a newer service/product out there - Profleetcare  https://profleetcare.com/   . It's a oil based product and really helps reduce corrosion. Offering several service's would help your bottom line / profit center.

ETA: Oh, this product reduces or eliminates mice or other rodents problems on farm equipment/trucks etc . . . . rodents do not like oily products.