i wouldnt.. if i was spending 30k on another s2000 you can pick up some very nice ones in very good condition for around that price. Haggle abit people are bound to drop prices down a little cause some of them have been up there and unable to sell for quite awhile now. and s2000's have chains not belts lol. And by unmodified to you mean cosmetically or mechanically modified? Check up some problems people have been posting up and look how much they paid to replace things to stop the "rear clunk" and what not.
But to answer your question again. 30k is alot for an s2k now so you'll find something alot nicer then what your describing.
http://www.carsales.com.au/all-cars/...s=61&silo=1011
http://www.carsales.com.au/all-cars/...s=61&silo=1011
Theres two white ones for under 30k lol. BUT you will find something alot better then what your looking at for 30k man.