There is always be factors such as mileage, color, and condition. If it is a white, green or purple colors, they are rare. The most colors you see are black, red and silver. You can always ask for a lower price, worse come to worse, the owner reject your offer. However, if it is the color you want, and the condition you desired, you may want to jump on without hasitation since NSX do move fast.
If it is a beater, you can factor in some of the potential repair cost. Service is not exactly a Civic and a good owner should keep the car service up to date. T-Belt, water pump and all other belts are extremely important. You don't want to get a NSX that is
Make sure when you test drive it, go through the following:
Interior:
Head unit and Speakers; make sure you don't have a burnt out speaker set (left and right)
Door seals
Roll the window up and down make sure it is tight
Seat leathers and dash condition.
Trunk and Hatch struts, see if they will hold them up.
Exterior:
Look for VIN stickers on all visible panels
Repaint is OK if the job is done right. Many NSX owners will repaint part of the car due to scratch, dent removal and rock chips.
See if all the panels are aligned properly.
Drivetran:
On earlier cars, it may take up to 10 minutes to warm up. After it is warmed up, feel the VTEC to see if it revs freely up to redline.
Check for clutch, make sure it does grip.
Also on early NA1, check for snap ring range. If it is, ask for proof if it has been fixed.
Other than the list above, they check out OK, you should expect to pay market value.
If there are mods, find out what they are. If the car is tastfully done, that's a very good bonus. If the car is weird parts on it, find out what they are so you can do an assessment if you ever need to put back the original parts.
Any one feel like to add to the list, please do so.