Here's the story you're going to get with an estate sale:
First, the machine will be priced ridiculously high.
Second, the machine will be "on", but only the GI lamps will be working, because 99% likely the batteries will have crapped out all over the MPU long ago. If anything shows up in the displays at all, it will be something similar to the Sys11 "ADJUST FAILURE".
Then you're going to find someone working at the sale and ask them if they know where the keys are. Most likely not, but if by some miracle they have them, you'll open up the backbox and find that corrosion-damaged board. You'll then explain to them how the game is not in working condition, and why.
And then, and this is the part that makes me want to smack every single one of these estate sale people upside the head, they will tell you, with a perfectly straight face, that they were "just playing the game yesterday". I swear to god, they must memorize that line from a script, and think we're all idiots and we're going to believe it. Doesn't matter what's wrong with the machine and what condition it's in, they were always "just playing it yesterday". The fossil who had the gall to tell me this weekend that an LW3 was "just working last night", with no controlled lamps and a non-functioning DMD, then proceeded to try to get it to work by pushing on the lockdown bar and the coindoor frame, so obviously she had no clue how to start a game even if it WAS working.
I have to stop myself from laughing out loud at these people because every time, without fail, on cue, the games were always "just working yesterday".