Cash and carry is the only way to go.
I went today for a Craigslist deal on a Space Jam near me.
He assured me it was in tip-top shape, and that he had taken excellent care of it. The seller needed the cash, but originally wasn't willing to take less. I made him an offer, which was a reasonable offer based on market, but less than what he paid for it, and he turned me down. Later, he came back and said he'd take that price. So I made the one-hour each way up there to look at it. When I got there, I immediately noticed a bad DMD. The offer that I had made was a fair deal, not a lowball offer, and the seller hadn't told me about the bad DMD, although when I mentioned it, he seemed to have noticed it as well. I asked him to knock $200 off for the DMD (it's not like I was getting a steal!), and he gave me the runaround, saying you could buy them anywhere for $88. Luckily, I had my iPad there and I quickly pulled up Marco to show him that this was not an $88 item -- Marco has them for $199+shipping. He said he thought we had a deal, I had already haggled with him, blah blah blah and he was unwilling to take less. He said I didn't hold up to my end of the agreement -- but I had! He hadn't told me about the bad DMD ($200 off the bat). Had it not been for the bad DMD I would have just given him the originally agreed price and taken it. But nope, because he was unwilling to fully explain the machine beforehand, I wasted my evening.
Moral of the story is... Your seller should be one of three things:
A) someone well-known on Pinside
B) someone well-known elsewhere in the pinball community, or at least someone who has multiple people that can vouch for their credibility
C) a seller who you may not have met before, but by combing the internet and playing detective, you can find plenty of information that corresponds with information that he has provided to you (WhitePages, etc.) and certifies them as a reputable person
My seller, in today's case, just happened to be none of the above.
Sorry if this was a little off-topic, but the point is that a cash offer in-person is really the only way to deal.