A well set up E/M is surprisingly reliable and my advice would be to pick up one that's been sorted out and well loved. Make sure you play it regularly

Watch a few Youtubes to work out what play features you want and browse the IPDB reviews.

I prefer later E/Ms to earlier....GTB wedgeheads in particular. If you can find a Spin Out, Sky Jump or Abra Ca Dabra, I'd say grab it. Also a Surfer, Card Whiz, Quick Draw or Outer Space/Orbit if you want a multiplayer .

There is a WMS Klondike for sale on the forums right now and I know that there's a really nice Gulfstream coming up soon here.

Beware...these things are addictive as hell...something to do with heating up bakelite or tungsten ash, or it might be the hypnotic call of a reset sequence