Could you talk to them, maybe show them some screenshots and see what they say? Actual pre-payments will be worth more than vague promises to pay in the future

Could you talk to them, maybe show them some screenshots and see what they say? Actual pre-payments will be worth more than vague promises to pay in the future. Being able to demonstrate real and specific value to potential users will be helpful in collecting dollars up front. Depending upon the nature of your product, creating a manual method to achieve the same results might save you a ton of development time while you understand customer demand.