By a cheap import the chances are it will last a few weeks and die, and have a look at how much RB parts cost, the key to keeping and RB25 alive is a PERFECT tune and an ECU that has a good knock retard ability, if its out and has even the smallest amount of detonation it will collapse the rings and most of the time crack the ring landings off which destroys the head, try buy a 2nd hand RB25 head
I have been raping my RB for 18 months now as an every day car and a load of drag and track events, and it still has a perfect 160psi over all 6, I have had odd quirks with the electrics, but never once had a mechanical problem.
Getting it to work well in an S chassis is not cheap though, there is a lot that needs to be changed and even when doing it yourself it still costs a whole bunch.
Unless you go el-getto, in which case it is semi cheap, until it brakes, which usualy doesnt take long.
I would suggest as a minimum that you change the timing belt, tensioners and water pump when buying an RB25,
