That is not a hybrid, that is a real mtb but may be as early as Mid 1990's vintage. I bought a similar bike at the time but with giant label on it. Mine needs a lot work due to my neglect of it. This one looks like it is in great shape. Be sure to take it around the block, check the hubs, headset, shifting etc. Those are not modern LX shifters, but if they work its worth it.
I'd bring 150 cash, but offer him 100 since it has the old shifters....