Just make sure you try and buy one with the basics already covered, otherwise it'll add up to "may as well just get a GTR" territory.
If you can find one with FMIC, full exhaust, boost controller, suspension, aftermarket ECU, and hopefully a few other extras for around $20k, that might save you $10k just there. That might make a budget of getting there below 35k possible.
Then your concerns will be building the internal strength of the motor, turbo and the required support systems for that. Otherwise, yeah, just find one already done .. it may be boring but it will save you a **** load of money.. over the last year or so I've seen quite a few GTS-T that will do mid-12's for $25-30k