There is a 2002 boxster up the road from me for 6500 and it looks every bit twice that value. We have had a Z3m, 996 911 cab, TVR, Caterham and a Mini Cooper cab and all have been great fun. Cheaper to buy in winter and then enjoy spring and summer. If you can then get something with a good working electric roof as so much more likely to use it. If you can get heated seats then all the better and a wind deflector is a must but can be found on eBay after. Boxster hard tops are good if you have room to store.