Man, tell the guy to fuck off.
A roady will cost you $80-$110 (legit one, more for dodgy) just to get the car put into someones name so you can drive it home, them (im assuming) you will have to get another roadworthy or blue slip in NSW to get it into your name. Plus like $30 in transfer fees down here, plus more up in your neck of the woods again.
Get him (or you) to write a letter for him stating that you have taken possesion of car RA65-XXXXXXXX, rego: ABC123 on the 6/5/2011 at 9.00am and any fines or similar incurred from this time are upon the new owner (your name, license number, etc.).
Then when you get it home, get your roady and rego it up there or whatever you need to do.
Saves some cash.