I have a 97 trek 6000 zx, its been my go to mtb for years, great ride, bonded frame!!! I changed all the components eventually except the seatpost and handlebars.
you should post a link to the ad but $50 sounds pretty good so long as the wheels are straight and the frame is intact.
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2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
2000 litespeed Unicoi Ti, XTR,XT, Campy crank, time atac, carbon forks