l am really interested in this kind of great machine but wonder if there is disadvantages that will bother me as now it is only available in second hand buy..
thanks..

that is the great machine and has won the best car in 1999..its perfect no disadvantage

If u r looking into buying a skyline then the best place to look & ask for info is on the Skyline forums,below r some free forums with owners Worldwide.
Owning any car has pro is & con;s myself have owned skylines for a good few years now & before that other turbo & non turboed Nissan cars all have been great cars & led me to buy another from this maker.
The skyline themselves r great cars & with the mix of great engines & handling gives alot to the driving experience,the GTR with its versions r great cars & offer a lot but other models r great also & should not be overlooked & at a cheaper price than the GTR versions also,non turbo & single turbo versions have alot of potential.the single turbo the more away from the rb30 conversions that is but the other engines r still great,the single turbo versions come as rwd & have hicas which can be locked off but has helped me out a good few times ,power wise these cars can see high bhp figures also the R34 GTT starting off at 280bhp stock.
Disadvantages r running cost as these need high octane fuel any less apart from any damage is the lack of power it will give out been there done that & thats on a high octane fuel but not high enough.
Parts wise there r plenty of breakers out there & Nissan still stock to my knowledge down to the R32 versions as l have used them for this plenty of times,also there r 1000 is of after market parts for these cars..
Regular service is needed on this cars.
l will add the buyers guide on a link but to read u will have to join the forum but as said it is free.
Worst bit about owning a skyline is the smile u will get when u drive it or just look at it which is quite often,this will make u look crazy but worth it & the times u make up silly journeys just to take the car out.

http://skylineowners.com/forum/showthread.php?t=69362&highlight=buyers+guide

http://hkskylineclub.com/index1.htm

http://skylinesdownunder.com/forums/index.php

http://skylinesaustralia.com/forums/forums.html

There r going to be badly modded versions out there & one without mods will be hard to find but 99% on modded ones will be with top parts & these cars love mods & to break the engine would take serious punishment given to it.And luckily most owners have spent that much on these cars the last thing they want to do is break them.Mine l almost keep in cotton wool.

l OWN 2000 NISSAN Skyline GTR-34 V-Spec II