Well as someone who has worked for different schools, teaches rally and off road driving professionally and does a lot of driving and instruction work for a certain manufacturer, plus all the events and racing I do I think there are a # of things to keep in mind.
1. Liability- I would have your p's and q's covered on that.
2. Billys- What are Billys? Industry term for people that turn up off the street to drive. A lot of people don't care about the car or themselves and all it takes is one second and you have a major issue. Plus few americans have any understanding of vehicle dynamics hence leading to more problems when you put people in a vehicle and let them go flat out, even in a "low speed situation". I've done a lot of low speed courses for manufacturers and even then you still always have to keep your finger on it.
3. Track maintenance- The rally course I currently use for training, we have to constantly maintain and it is expensive and time consuming. Rally cars, even at low speed, having run over a course a number of times will rut and damage a course quickly. Also rain will rip up a course and if used in the wet and not maintained it will "set" when dried creating some interesting scenarios.
4. The Track- I would put a lot of thinking into how you set your track up. How much sideways action, how much speed, how much run off room, etc. Again liability and safety come into play. What if someone misjudges a gas pedal for the brake? I've seen it happen with devastating results.
5. Instructors- If you have instructors ride right seat make sure you have skilled instructors that have an understanding of vehicle dynamics and can also recognize things going wrong in car before they do. If you don't have instructors in car, my only worry is that people can turn it into a demolition derby.
6. Car maintenance- cars will take a beating. Gravel blasts metal on the underside of cars to pieces, tires get ripped up, front and rear clips get beat up, etc. Not to mention all the mechanical components with Billys revving engines to 9000 rpm or crunching gearboxes and smoking clutches.
I think you have a great business idea, but I hope you consider the above and keep that in mind. I deal with these things all the time in the course of my work. From reading what you wrote, I have good reason to think you don't know what you are letting yourself in for and with $50K it is going to be tough.
Good Luck!