Holy rust!!
....DW does not look like it is in a house where they wash a lot of dishes, LOL.
Or anything else for that matter. Look at the floor and cabinets surrounding it. Having said that though, I picked up a 20 at H4H that looked awful on the inside and outside. It cleaned up beautifully and has been my daily driver for close to a year now. It's a great machine.
The inside was terribly stained from hard water which cleaned up nicely. The racks were in decent shape and I eventually replaced them. I would take a peak at the inside and see how it looks. And, if possible have them run it for you and hear how it sounds.