There good cars, just remember they are a ageing model and the most of the motors have being stressed so more often than not a few dollars can be spend on maintenance. Keeping it as a weekend or track car is a great idea, using them as a daily tends to cause a few more issues. Value for buck you can't beat a GT-R in terms of performance, just shop around and get a straight one, general things like checking the compression, chassis, leak down tests and general inspection by a independent workshop are some good starting points when shopping for one.