I would just walk, no run away from this dude! He's just dicking you! For $9k it should not have any rust, the window fixed, and for sure a "custom tailgate" that isn't just a piece of diamond plate thats bolted to the body! He must of got hosed and is trying to recover his loss from somebody else! I had a buddy sell a fj40 with a lift, 35", 350 small block, custom killer exhaust that was "Oh my God Loud!!" full hardtop/soft tops with doors, and the only thing it needed was a paintjob! All the metal was rust free, all new seals, and some things I'm forgetting. He sold it for $7k!
Make him an offer if you want it, and just let him know this is my offer!
Are you willing to wrench on one then get one that's not as nice but affordable!