bring the cash, yes. but do your homework: establish that the person you're visiting has an established presence here. read some of their posting history. if they're an active member of this community, it's unlikely they're a scammer or thief.

both of my in-person transactions with other pinsiders were very smooth and very friendly. (shout out to habo and hank527 -- top notch dudes)

we agreed to a price beforehand. i showed up with cash in hand. as long as the machine is as described, haggling at that point is bad form in my opinion. i played each game for a while to make sure everything was kosher ... (and both pinsiders invited me to hang out and play some of their other pins as well) ... and then i handed over the money and we wrapped and loaded the game.

I don't think that's pinside's fault. The general state of location gaming, the rise of home game rooms, and the passage of time have changed pinball a lot.