I mostly agree woth above advice, except the dont buy a project part. My first pin was a 350 dollar project that I took down and completely restored- a two player late 70’s Gottlieb.
IF you are a electrically/mechanically inclined individual that wants to get your hands dirty an EM is a wonderful playground. It will be frusturating as hell and you will probably call me an idiot at some point if you follow my path. But the reward is amazing and you will be forever on the look for your deasired game in any conditon- knowing you can bring it back.
Take care in being honest about if thats for you. It could be a year before your game is up and running or longer (my latest two games have been being restored for over three years) and there will be many painful moments of sheer frusturation.
If you historically have always paid someone to fix your stuff and are not naturally inclined to find information and teach yourself something new for a hobby (perhaps you get enough of that during the day- whatever) spend more than the above recommendation to get a reliable game and enjoy playing the hell out of it. It will eventually have a minor issue and if it was 100% before hand- it will be easy to diagnose here and fix yourself and you will get a very gentle introduction to game repair and maintenance.
One thing for sure- you can identify a clean EM easily because they are so old they will all be dirty sticky messes unless someone went through it.
My true buying advice- drive and inspect the first five pins you see advertised regardless of title or conditon. Learn what an EM looks like, learn how to pop the glass and get under the playfield (many selling dont know how or are uncertain) learn how to get at the backglass and the head. When you have seen 5 games and can inspect one and have a frame of reference- you will know when a clean one shows up and also have a vague idea of price.
Beware- at least around here- on local adds most people price EMs insanely high- an EM priced anywhere over 1K should be either a top game or have had a very through going through and be clean and 100 %. FYI. New rubbers and LED bulbs is not a shop job.