Ive seen R34 4 door sedans GTT (yes turbo) go for 18-21 grand on J Spec site, add another 1-2 grand for tyres and other hidden costs and you have pretty much a low 20s cheap skyline, the only catch is they are not manual.
1998 Nissan Skyline GT-T sedan
2.5L turbo
Tiptronic
Black
36,000 km's
No major accident history
Power steering
Power windows
Air conditioner
ABS brakes
Dual air-bags
Sunroof
Keyless entry
CD player
Scrape on passenger door
Auction grade 4, good condition
... 975,000 yen FOB .. around $20,900 landed AND complied
http://www.j-spec.com.au/list/index.php?ID=4349
http://www.j-spec.com.au/list/index.php?ID=4341
http://www.j-spec.com.au/list/index.php?ID=4339