Yeah, I’ve seen those tricks. The risk is twofold: first, the counterfeit‑detecting agencies will sniff you out if you start flipping every bill in a shop, so you’ll have to move quietly and keep your trail clean. Second, the “codes” are often misdirection—what looks like a pattern might just be a watermark you’re not meant to read. So keep a ledger, don’t share your find with anyone who isn’t absolutely necessary, and always weigh the value against the cost of being busted. A careful eye, a tight plan, and a backup exit strategy is the only way to stay in the shadows and still make a profit.