I grew up on a prep school campus and it is a great lifestyle. It's sort of like living on an all-inclusive resort but without the free booze and beaches.
First you need to distinguish between a regular private school and the elite prep schools. The elite prep schools pay a lot better - comparable to public schools or even a bit more. But you have to work hard. You have a full teaching load plus coaching sports plus dorm duty at night a couple days per week.
But on the bright side you can live on campus rent free while you buy and then rent your house. You get all the amazing facilities including a beautiful gym and private track. Most prep schools have a nice woods area where the cross country team runs and you can take your dog for walks there as well.
Classes are small and the kids are bright and highly motivated.