Informal equity agreements

Hi all,

I'm doing a startup and I feel we need to establish a basis for equity distribution before we get too deep into the project. My partner is hesitant to sign a formal agreement before we get a good sense of who's putting in the most work, as we're all still in school in different places in the world. Would it be possible to sign an agreement that would establish a basic range of equity: like no one partner can get less than X percentage until we are about to get funding and sign an official agreement?

He's insisting we wait, but perhaps if we get something in writing it would be something that could hold up in court. I trust my partners - I do - but I think it's wise to establish something from the very start.