Hello,
914. Well i think you have to differentiate between a 914/4 and a 914/6.
I would say the 986 is a future classic, because Porsche is interested that it will get a classic Porsche car – just because Porsche Classic centre is interested in doing business.
Also Porsche always raises part prices for Classic Porsche cars. So maintenance is getting expensive, which also means maintenance prices raise and that means car prices for good cars stay stable or raise.
Will the value raise? Edition cars always raise a little bit more than the "standard" cars. So a 986 550 Spyder might be a good choice.
But if you take a look at the maintaining costs i'm not shure if it is a good invest. I think if you drive your car you can throw around 1.000 Euros of maintenance costs in your car yearly (tyres, brakes, oil changes, general maintenance). And every 10 years i see an investment of around 5.000 Euros (clutch, suspension, water pump, generator, condensators, convertible top, rubber parts and all the other stuff that can break). So in 10 years you'll have an invest of 14.000 Euros. Plus taxes, insurance, fuel, garage rent and so on. Plus inflation.
So if you put the car in a car collection and wait, maybe you'll get a little money out of it. But f you drive it you won't. But you will have driving pleasure.
And at the moment i see a bubble in Porsche prices over here in Europe – mainly caused by low bank rates. So people try to invest in goods.
Regards, Markus