- You never hold stock. Customer buys from you → you forward the order to a supplier → they ship direct to your customer.
- Your margin is what's left. Sale price − (product cost + shipping + ad cost + platform fees). Ad cost is almost always the biggest line, and it's the one beginners forget.
- You're running a marketing business, not a warehouse. Most of the real work is finding cheap, targeted attention — not picking products.
If you can't sell it for at least 3× your landed cost, ads will eat the whole margin. Test it below with your own numbers.