Use the power of the INET.
Check KBB values for the car at
www.kbb.com. Check Private Party values to see where this guy is.
Second, do a sort on Auto Trader.com and find some comp cars that are in your area.
With these two pieces of data, you should be able to understand where the car is in valuation terms.
The real issue is CONDITION and HISTORY. You need to have these checked. Never buy without a PPI by a Porsche dealer and a complete understanding of the car's background.
Good luck.
PS-sounds expensive to me but I don't know the values on the East Coast.