I know the trend today is to tap this, click that, swipe this other thing, Paypal her. Anything but cash! The paranoid (or wiser) among us will say that the govt types want to eliminate cash so they can easily track everything we do at all times. Maybe yes, maybe no. To each his own.
In any case, don't overcomplicate things. If I don't know someone and am selling them an expensive pinball (or anything), I want cash and cash only. And I will be looking over the bills carefully to make sure all the holograms and strips are where they should be.
When you make the sale, keep the cash around the house somewhere. You can find a good place to put it so the casual burglar wont find it. Now the next time you buy a game, you will have most or maybe all of the cash you need.
If you deposit the cash in the bank, it sounds like the new laws may result in you getting a letter from the gov asking why you did not report the money as income. This was always true with large deposits, but will happen at significantly lower numbers now. This will require everyone to keep detailed records of what we bought, how much we paid, how much we put into it during repair if any, the selling price, and the profit or loss. This will be more than a little pain in the butt, needless to say. It will probably necessitate setting up a formal business if you sell more than a game or two a year, allowing lots of write offs on the plus side.