Welcome aboard, young timer, from all us old timers!
Tip one: make sure you play the machine before purchasing. While software like Visual Pinball will give you a good idea of gameplay, you really have to play a pinball machine to know if you like it or not.
Tip two: Unless you really know what you want and they happen to be high-end machines, then I would try to purchase a couple of cheaper machines ($1600 to $1800) to begin with that you enjoy playing. That way if one needs fixing you still have a second to play on while you work out what is wrong. You can always move them on later.
