We currently have two models. One is pay-per-prototype deal, we pay $2k-$3k as upfront payment to developers before the testing stage. Another is monthly payment, we pay fixed amount of payment every months to developers, and they will give us certain amounts of prototypes for testing, and the monthly payment is the development cost, not upfront. For example, we currently work with a developer with an offer of 8k monthly payment, and two prototypes in each month.