dude, if you're 17, noone will insure you for a GTR. If they will, it will be about $10k/year..and whilst driving an R is cool, there's no way once you add fuel, maintenance and mods that you could decide it is a good thing to do.
$10,000 p.a. insurance = around $200/wk
so, weekly GTR budget as follows, assuming you own the car outright!
$ 200 - insurance
$ 50 - fuel
$ 30 - maintenance
$ 60 - mods?
So, just HAVING the car adds up to around $340 a week or $680/ftnight.
I reckon you'd be better off finding a couple of nice private school girls, feeding them full of drugs and piss and thrashing them three ways every friday and saturday night...
better still, be realistic. if you want a fast/flash car spend $18,000 on a spastically quick S13 and own the road with pop-up headlights and a roll-cage.