CardFlip Ledger: A profit-tracking webapp for flippers records buy price, marketplace fees, shipping and the realized sale price to reveal true margin per card.

Build a simple buy/sell log with fee presets for the top four marketplaces and test it with ten active flippers.

Why it can work: Most flippers guess profit because marketplace fees and shipping quietly eat margins; a ledger that shows true per-card profit fixes the number-one leak in the hobby.