They are older men at the mall that hang out and wave $20 bills at you for a few minutes of your time, then they trade you to the next guy who is waving $10 bills (Notice decreasing value) and that guy does the same thing in turn. I do not know about the guy at the dumpster, but do remember that dumpsters have handles so it could be a nice brace for day trading to happen.
Just look for the guys in fuzzy purple hats with the gold cains, they are the mall day-trader MM's.
Don't forget to take your knee pads for the day trading, you will thank me later.
“I got a great deal on some French WW2 army surplus guns. Never used and only dropped once...”