Ok, so you have a dealer...does he have a sales lot. New way of selling cars is from home. Get a dealer license and go to the auction and buy an auto then list it on craigslist or e-bay or auto trader and find a buyer. Since I know what I am talking about you can bet this is a $2-3 pounder, which means, he can make $2000 to $3000 off the car. I wouldn't waste my time on a $100 or $500 sale, no way. So, he really doesn't know anything about this car and you said there is no paper history, this should alert you. No auto sales company will let see this kind of paper work. Scares most people away.
Yep, it's a 2 owner in exceptional condition...come see for yourself. Then you get the potential buyer excited in touching and driving the vehicle which makes a personal bond. Bang, you're hooked. Don't make it personal...yep, it's a nice one but just a little out my reach and I'm a little worried about the mileage. This is when the sales start...well, maybe we can come to an agreement, I can give a little. Remember, it has 100K on the clock, so, you have a lot of maintenance for the future.
I looked at the images of the car and it looks like it's been taken care of, and since it's CA car, you folks do a lot of highway driving, that's good. A Porsche likes to be driven, not sitting. The TIP is a plus for me...the IMS problem is more with the sticks than the TIP's. I would tell him, I have a small Porsche shop, not a dealer, that I would like them to look it over and give me an assessment of what I may need to do in the future. Also, you now can see under the engine for leaks, etc. You can tell him you're DIY guy and you just want to get a handle on what you may need to do right after you make the purchase. Make him feel comfortable about your concerns, and proceed from there. If he says no...walk away or tell him, ok, I will give you $7500 cash. He will turn that down...well, what did you expect, I need to know what I am getting into.