Well to start I?m from Utah pretty close to the motor sports race track. I?ve been working on cars since 14 with finishing my first complete big block build by 15 so I?m pretty comfortable under the hood. As far as build type I was thinking daily/ Track monster.
Also I?m married with 2 children and working on a 3rd I?m planning on taking my time one this build over the next 5-6 years.
But if you're comfortable with cars, theres less risk in the purchase of a used STI!...especially if you plan on building the engine, as you'll easily be able to notice/fix any internal issues.
The big thing with these cars is that people mod the crap out of them without knowing WTF they're doing, and end up causing damage. To compound that, people will often return them to stock or near-stock form when they want to sell--and you end up getting a car with an unknown history. Obviously unknown history is the deal with many used cars, but due to the level of mods that many get, its more pronounced here. So lets get into it, shall we!?
A daily/track monster is a bit of a paradox! And you say 5-6 years for a build. You could pretty much get any STI at that rate, totally build out the engine, and not really worry about its history so much. But I don't think that's what you're looking to do. Keep an eye on Bring A Trailer, as STIs get posted there every now and then, but usually a bit older IIRC. And if you're not afraid of the mods, I would look in the classifieds on NASIOC and IWSTI as you can often browse someone's post history and see what sort of person they are and the way they treated the car. Personally I'd stay away from dealership trade-ins UNLESS it's a Subaru dealership since they'll be much better at spotting the issues and knowing if the car had been modded or not.
Then there's the build. For a true track monster you're going to want a big turbo you can keep in spool at high RPMs. Unfortunately, for street driving you wont be able to get any boost without driving like a hooligan, so it'll feel really sluggish. It's pretty much opposite design philosophies! So you'll have to think about your sweet spot for power to balance driveability and track prowess.
Have you tracked cars before? I'd love to hear more about your experience!
Ok, that's all for now, gotta get back to work!