What do I think?
You're mentioning that's a web project. To make a reality a web project shouldn't cost a lot. Thus, the two founders should be able to put their money to make this a reality. Of course, talking about an MVP, a further developed product at this stage isn't justified.
IF for some reason, the two founders are not able to come up with the resources to fund this, then without the web development there's simply no product. Thus, this developer becomes essential to the endeavour. IF the founders are not able to pay anything to the developer while he/she makes the magic happens, then the fair share is 33% for each member of the company: the two founders and the developers.
Without the developer there's no project. It doesn't matter how good the idea is.
You guys are founding a company, those are the compromises that had to be done in order to make this project come to life. Even if you find someone that's willing to work for 2% with no salary, on the long run you'll have motivational issues, specially if the project is a complex one.
My suggestion: Get the money (preferably from your savings), outsource the developing with clear goals. Then launch it as fast as you can. Launching it's not the end of the game, it's the beginning, so the faster you reach there, the faster you'll see how this will evolve.
Best of lucks!