[Gogar]

My opinion:

If you buy a 100K mile carrera to $15K today it will never be less in the future than it is today.

IF you don't put any miles on it and cover it up all the time.
IF you keep the tires, rubber, leather, fluids, and mechanical stuff in Tip-Top shape.

THEN, in 5 or 10 years pull it out of the garage with the same 100K miles on it and you'll probably MAKE some money.

But what's the point?

I think SCs are at the bottom of their depreciation curve, 84-86 Carreras are not far behind.

The biggest thing to think about is not the overall value of the car, but the cost of ownership which - with these cars - is either VERY affordable or VERY expensive, depending on your diligence with the car and a lot of luck.