same thing happened to me once, then i woke up!
the obvious things to look for is wear - ways, screws (although if you are converting that won't matter) spindle bearings etc. Even if every surface & bearing is shot its still a great deal for free! There is nothing that cannot be restored and even if you threw everything else out, it would still be nice set of castings to start from for making a cnc machine
once you have a mill of this size you won't want to give it up. You might find yourself wanting to use the mill to make cnc mill rather than convert it because it's so darn handing having a heavy (by home standards) manual mill around the garage!