Short notes on reading a product and a COD ledger. Not a course, and not income advice.
Start with delivery rate, not the selling price. A wide gap between cost and price looks attractive until refused deliveries consume the dispatch fee. Compare estimated profit per delivered order after that fee. If you cannot explain the product in one sentence, the listing will work harder than the unit economics.
You fund a batch before the customer pays. The courier collects later. Only delivered orders become revenue, and that revenue sits pending until it is reconciled into available balance. Treating pending money as spendable is the usual way a reseller account goes tight.
Instagram, WhatsApp, and a website do not share a delivery rate. A reel audience and a repeat WhatsApp list refuse orders at different rates. Run a small batch, write down what was refused, and only then raise the order count in the calculator to something you have actually seen.