You get what you pay for.......
Personally if you are preparing to spend less then $20K on an R33 GTR, I think you will struggle.
Realistically, for something that won't give you ongoing trouble, $30K is the minimum you should budget. If you spend less on purchase, you will just spend it a bit later on repairs and maintenance....
If you can't afford that as a minimum (and remember to budget for ongoing costs like insurance ($1000+ p.a.), 98RON+ petrol ($100+ per fill), regular service and fluids ($300-400/qtr), rego etc....) then stay away - you'll just be dissappointed......
If you can afford it - its the best car owning experience there is.....
to buy a car - I'd recommend importing from a reputable importer (see separate thread) - it's your best chance to find something meeting your taste,budget and requirement.
Good Luck
Cheers
The Baron