What is the best way for a PSD designer to team up with a Wordpress theme developer on Themeforest?

I am a PSD theme designer. What is the best way for a designer to collaborate with a Wordpress developer? I mean what is the best way to share profits, send/receive money etc… I would greatly appreciate responses from those that are currently in design/dev (PSD/Wordpress) collaborations. Thanks a lot in advance!

The start would be uploading few items ( PSD ) to your account as a reference.