Some misc thoughts on buying from a stranger which should be obvious but maybe aren't to everyone.
1) Cash is usually a necessity. I don't trust any other method of payment if I don't know the buyer and many people are the same, especially if you want to negotiate the price to a lower number. So you really need cash to complete many sales. Therefore, you must be careful.
2) If you are looking at an expensive game, maybe thousands of dollars, but the address is in a poor section of the area...do you really expect to find a 5 thousand dollar game in a trailer park or inner city ghetto where the houses are the size of postage stamps? Anything is possible, but risk goes way up. If you still think the deal might be legitimate, start asking a lot of questions about where they got the game, how long they've had it, any condition issues etc. Ask somewhat technical questions that only another pinball collector would understand and give a sensible answer to. If the answer makes no sense, then you know what's what.
3) Use common sense and Google street maps if you are not sure where you are going. I personally didn't go to a clearly ghetto neighborhood in nearby Wilmington Del where a supposed mint MM could be had for $6000 cash. Most of the cars that appeared in the street pics weren't worth $6000, let alone a pinball machine. I would have almost certainly been held up and robbed.*
3) When I am taking a load of cash to an unknown house to look at a game, I try to arrange for a friend to go with me, and where legal, both of us are armed. Even then, if you pull up to the house and it looks like 4 or 5 gang members are waiting to show you the pinball, or the house looks abandoned, or really run down, keep driving! Again, it might be legitimate, but odds are starting to go way down. No pinball is worth your life!
4) And finally, the most obvious of all - if it seems like a deal too good to be true, it is probably a scam. Everyone gets a great deal once in a while. But that is probably a desirable game that is maybe a few years old and is not working quite right. The kids have grown up and the parents are moving. We all know that story. But NOBODY gets a top tier, "A" list game for $1000. It just doesn't happen! Unless the seller has one heck of a believable story to support why they are selling an Addams Family for $1500, don't fall for it. EVERYBODY looks on Ebay, Pawn Stars, and everywhere else they can think of and has, if anything, an over inflated idea of their game's value. Few people are unknowledgeable to the point where they list a game for much less than its worth. Exceptions occur, but are few and far between.
* I did have a little fun with the seller who sounded on the phone like a younger 20-something male who didn't know a lot about pinballs. I told him I would be down that day and planned to bring help with me to move the machine. The guy assured me his "friends" would be there to help me so I didn't need to bring anything but the cash! I responded that I didn't mind. I told him "the other Troopers from my State Police barracks were off duty with me that day so I planned to bring 3 or 4 other State Troopers with me since they were all big strong guys with nothing to do for the day." (I am not a State Trooper, but this story amused me and I wanted to see what the reaction would be!) Suddenly, the "seller" got very evasive about his availability for later that day. In fact, he suddenly wasn't sure he would be available the rest of the week! I never did go to look at that game!