Be careful. "Saying" they'll pay and them actually paying CAN be a different thing believe it or not. Consider yourself testing the market till you ACTUALLY take money from a few customers. (caps for emphasis: I've been burned before)
I think I would have to have a MVP before getting any early adopters cash though, right?
Have a look at this mixergy interview for some ideas/inspiration - http://mixergy.com/sam-ovens-snapinspect-interview/
Think of it as a form of freelancing where the customer just wants some end result but doesn't care about the code itself.