If you're starting a marketplace, you need to fill your supply side. But chances are, you're not able to immediately get tons of suppliers on board. That's ok! A good way to validate supply is to "fake" it. This doesn't mean not having actual supply, but creating that supply yourself. So if you're creating a marketplace for outdoor and hiking gear, renting or buying up some small inventory can be a good proxy for actual suppliers, both to have activity on your marketplace and to entice new suppliers to get on board.