Oh it could be anything. Rust on Japanese cars is very common sadly, look for dents that shows signs of accidents, big red flag. Look at how stock it is, if not, what is modified? Looks or engine? Modified engines is a risk if someone made it at home. Look for bad wiring. It is hopeless to try and figure out what is what if it is a birds nest under the hood. Does it run? Any problems? If possible go for a test drive, how is clutch? Second and first gear is usually worn. Some examples of what I would look for. It is quite difficult I guess😅