I know you probably came on here expecting us to say that it's a good idea to buy the car and so on and so forth....
But realistically, we're only telling you the things you've already heard from everyone else you've asked. So theres no point getting shitty.
If I were in your position, I'd prolly buy a Mitsubishi Galant VR-4 for under $10000, use the rest to put a knock policy on it, rego it and give it a general clean up.
Pros:
-VR-4's are an awesome bit of kit, so you wouldn't be driving a shittah.
-You can still get an insurance rating on a knock policy.
-You'll prolly have some change for maintenance, insurance excess, running costs etc.
Cons:
-You're inexperienced, so you may end up hurting yourself, or worse, someone else.
-The car may get stolen, but $10000 isn't that much on the scheme of things.
Thats about as rosy as its gonna get.
Oh, and just because most of us drive skylines now, doesn't mean we've never had to drive a crap car. We're all talking from experience, so you'd do well to listen.