Like a few people have said before me, i wouldn't go for any cheap GTR's, as you get what you pay for.
We bought an R32 GTR about 3 years ago and at the time the 18k GTR's of today were 23k then, and soon after purchase ran into many problems and if it wasn't for my Dad being able to do all the repairs/work himself, it just wouldn't be feasable to afford repairs, maintanance, parts etc. He still says, 'we should of spent 30k' on a GTR. After 3 years and lots of $$ spent you still encounter problems like CV joints, belts, brake lines, engine hoses etc etc, not to mention the wear on the engine, gearbox, suspension, etc etc etc.
Do yourself a favour and save some pain and buy something decent and do some research into what you should be looking for when buying one. Money spent now will be wisely invested to save you money down the track when the inevitable will happen to an 18k GTR.