Suitable is anything with brakes good enough that they don't fade over the course of a day. I've never rented a car from Avis or whatever and taken it to a track, but I hear that people do it all the time.
I race an ITS prepped 2nd gen RX-7, and have a BMW M-Roadster that I put some race pads on when I go to the track. The Mazda is way more fun because of the stiff suspension (race rubber adds a lot). I also like being strapped in so I can focus on driving, not staying in the seat. Still, the roadster is a blast.
Any money I spend on the track day is money I will not spend on my normal race season or race related stuff, so less cost is better. I don't think I'd spend $600 a day on a Ferrari (based purely on the last time I had to rent a car in Vegas, I looked into it). Then again, I don't know what the going rates are except I could get into a Skippy RT-2000 for about $900 which includes rental of the car, track, and free advice from a number of instructors.
Is the Wabbit equiped with farfegneugen?
Steve