I knew a couple guys who had a nice operation at a grocery store. One worked in produce. The other shopped and left his full cart by the back stockroom door. Then the guy in produce would pull the cart in the back and pack all the empty produce boxes, call the manager to open the back door for him to toss his garbage, which most of the produce boxes were waxed so couldn't be bailed with the regular cardboard. Then he'd go on break, walk out to his car which he parked on purpose before his shift, and unload the dumpster.
This was back in the days before cameras everywhere.
They were making $800/week on selling at the flea market. Not bad for working a $3.35/hour job. That's 6 times what he made a week in his paycheck before taxes working part time.