After restoring a few machines stored away for decades without idea of their condition or even if they ever worked for the owner -- my advice would be to pick up a machine that "used to work" over something happened over a mystery or partially hacked machine.

A machine that was playing for years and then suddenly dies in the home of someone who has no technical skills can typically be an easy fix. Stuck score reels, broken EOS switch, loose wire, dirty contacts etc.

Harder to fix is that mystery machine found in a storage locker and sold after the owner dies. Who knows what the history of the machine is, could have been partially parted out, hacked at by someone who didn't know what they were doing, hopelessly rusted up from poor storage conditions etc.

I picked up a couple of "bargains" like this and got them going but it was very challenging.

Definitely look at the playfield condition and see if a replacement backglass/plastics are available.