It is always important to either view the game in person, have many good photos of the game, or have someone look at the game on your behalf. It has been a buyers market for almost 2 years now, and there are genuine bargains out there.
Most buyers fall for the usual "too good to be true" deals. Watch out for sellers that say ;
"The is a switch problem that will be a simple fix" - If it was a "simple fix", then why not FIX it, or have a knowledgeable technician repair it so it can be sold "fully working". I recently saw a game that had a "simple switch problem", and it ended up being a costly board repair.
"we replace blown globes and rubbers" - So does everyone else, but it is NOT clear if ALL globes, or ALL rubbers are replaced ? Same with coil sleeves and pop bumper skirts.
EMs are usually cheap, but be aware of missing coils, relays or ever score motors.
As a first machine, you should look around at the different suppliers and play each game that interests you. You should buy a fully reconditioned or restored title and then buy a project game of the same manufacturer to learn from.