Quoted from Timerider:"... for a decent price?" -- you're about 8 years too late. You have to be lucky, and find that estate sale/Craigslist/Facebook ad and swoop in within minutes, always have cash & tools & vehicle at the ready. (It's cut-throat at times.)
Just finding a project machine in the first place is difficult, for me at least. All the pinball machines I browse for have already been restored. The only ones that pop up are the generic themed EM machines.