1. You add products you'd like to feature in your competitions
2. Customers purchase a ticket and select a number
3. The competition is is finished and a winner is selected (Either automatically by the website or at random by yourself)
How do you make money?
Product A costs you £1000, you sell 200 tickets at £10 each (£2000 revenue), minus product cost = £1000 profit.
The beauty about this is, you don't have to own the product before the competition ends, so could pay for this once the competition closes.