The Fork has been replaced.. note the length of the Steerer tube above the frame... that fork will weigh about 5 lbs or more. . The fork is a RockShox Judy... they work ok. Parts can be found with some digging around... simple and dependable, if cared for.
The Frame is a "Small" size... if you're under 5'6" you should be fine on it... Maybe up to 5'8", but it'll be too short, front-to-back..
the 4000 series frames are light and strong.
the X9 parts are a nice upgrade, but the stock deore rear der. would outlast the X9 2 to 1.... the cassette is larger than stock.. crazy goat gears when combined with the front triple crank.
i'd have upgraded the crank to a Hollowtech, and upgraded the fork to a Reba Air fork.
the front hub has been repacked, so the bearings need to be checked..too much grease was packed in there. Shimano 475s hold up fairly well, but tend to get water in them...
swapping on either discs or Koolstop Orange pads will make the bike better in wet conditions, and make it easier to sell in the future. Shimano MT200 Disc calipers/levers go for under $75, and discs are 15 each or so...
the paint looks pretty good.. most of these get hammered and tossed on the ground as the younger riders learn about riding.

super fun bikes, worthy of a few upgrades. tight trails are a riot on these.
$200 to 250, US.
wave $160 under his/her nose... work from there. Put the savings towards disc brakes.

Edit: the fork might be ready to replace anyway... looks like maybe it's worn, and grease is working up onto the chrome legs...use that in the negotiations, and drop to a $140 starting point... the chrome might have rust pitting, or can wear completely through... the bushings wear out after a lot of use... a rebuild then costs more than a good Rock Shox Reba take-off... and you can find Good Rebas for $100 or so on CL or Facebook.