[jluetjen]

Chris;
I've rented some race cars (SCCA) in the past and have made the following observations.

1) Legal stuff -- AKA: Contract
a) Sure, ideally it's a gentlemen's agreement, but make sure that the customer understands the details by having them signing a rental contract that clearly specifies the liabilities.
b) The liabilities work out like this from your perspective: Heads I win -- tails you lose. If anything goes wrong the customer pays. If the customer gets hurt it's the customers fault. You have no liability for anything whatshowever.
c) "Racing is a dangerous sport. Participants can gete injured, maimed or even killed. etc.etc. etc" None of this is your fault nor do you take any responsiblity if it happens.
d) In spite of points a-c above, always try to make good on ensuring a positive experience for the customer. Sure -- everyone says that, but few do it. If something breaks (and it was your fault), don't stick it to the customer even though the contract says that they are liable. You seem like a fair guy so I don't think that this will be a problem.
2) Pricing -- Target maybe 1/10th of the purchase price of the vehicle as a ball-park rental charge. Keep in mind that it includes all of the consumables (brake pads, oil, a portion of the rebuild costs, seat belt usage, etc) in addition to the cost of the vehicle. Also don't forget the fuel unless you have the customer pay for that out of their own pocket.
3) Experience -- A real differentiator will be to make it the "realization of a dream to drive a real Porsche race car" for your the customers. I've rented an ITC Chevette (hey! Don't laugh!!!) which was dog slow. But it was fun because the owners made me feel like a star driver. The other thing was the car was reliable and handled and braked well. (Unfortunately the valves floated at around 5000 RPM which acted as a rev limiter.) Compare that with a Spec Racer rental I had where the car was competitive but handled like a pig with massive corner entry understeer. I asked the mechanic about it and what sort of set-up he had on the car and his response was "Go ahead -- look for yourself". I've never been inclinded to race a SR's since then even though I had a good finish and got a placque.

I've got some copies of contracts filed away. I'll see if I can dig them up for you.

BTW - The black car is a good looking product. What's the spec on it?