My advice is to do a compression test and leak down test before purchasing the car. If that comes out okay than your engine is fine with OR without a boost kit. I bought mine with a supercharger since it is a much better deal. The stock NA1 nsx is slow by today's standards in a straight line. Unless you rev it out and red line it everyday you won't get much power out of the engine. 90% of the people who track their cars don't even push them to their limits are even close. As long as you have someone check the car over you should be fine.
Personally, I wouldn't buy a stock NSX unless it was a late model NA2 that you plan on garaging and never driving. If you plan on driving it than get a low boost kit and have fun. I live in Las Vegas, NV with with hot weather so I am adding the standalone EMS and the air-to-water intercooler from Science of Speed. That is important since the charge temps get pretty hot on the SC kits.
I know plenty that enjoy their car with no boost and think it is fine. Then again those people don't drive their car at all really.