For many of us, fixing the odd fault on a pinball is part of the fun. Are you used to soldering irons, multi meters, fixing stuff .....
if you are new to this I would suggest caution. Pinballs are hugely complicated. Folk like me rely on one thing at a time failing. I can diagnose this, and with tips from the forum, I can fix it.
But if you bought a game with multiple faults, it could just overpower you.
Folk on eBay and gumtree can be sound. But they can also be dishonest. Stupid. Or dealers flipping routed games after just giving them a wipe. Your best bet will be an enthusiast's game from here. Enthusiasts often fix everything. Folk like me get a game and then go through them fixing all the mechanical and electrical problems, replacing broken bits etc etc
I phoned about a game on eBay and the guy said " I never remove the glass from a game" with pride. Warning sign, unless it is a rich owner who gets experts in to maintain their games. Games like this can have loads of faults as the owners do not fix them. I asked him to turn it on. I asked if there were error messages on start up, he said "no". But I could hear the beep, beep, beep, beep that wpc games make on startup when there is a diagnosed fault. So I forgot about this one.