The best place to find nice, home-owned or at least well taken care of machines is through
Mr. Pinball classifieds. You'll find all the major machines listed and in a variety of conditions, depending on what you're looking for, (from beat-up route machines to home-owned only).
As far as repairs go, they do break down from time to time no matter how well shopped a machine is when you get it. They are incredibly complex compared to something like an arcade game, and unless you enjoy fixing something for the sake of fixing it, you'll want to have the number of a pinball tech that can take care of repairs (or better yet buy a machine that someone will warranty or at least provide service for a price).
A few places not to buy from: Ebay and Super Auctions. Buying sight unseen from Ebay when you're new to this is not a good idea unless the machine is local. Shipping is expensive and can cause problems if not packed properly. Super Auctions has terrible machines that have been abused on routes and usually have some kind of problem that isn't apparent to first time buyers. The commission they charge is extremely high and they end up being horribly overpriced.
For manufacturers, Williams makes the best machines by far. I would avoid Data Easy, Sega, Stern, etc. The themes look good but the gameplay is usually crap.
Some good machines for people that don't want anything too difficult but is fun right off the bat (and I'm guessing your parents probably fit in this category): Theater of Magic, The Addams Family, Tales of the Arabian Nights, and Circus Voltaire, with Theater of Magic #1 by a wide margin. These are all top notch games, although they might run you a few hundred dollars more than 3k.
When you buy something, you'll want to a machine that's just been shopped with rubbers replaced, playfield waxed, that sort of thing. Ask the person you're buying from what he's fixed, replaced, etc. Buy from a collector, they're usually fanatical about the hobby and usually sell better games than dealers do.
If you have any questions just send me a PM.