Check out the 'founder's pie' calculator (google it) not a perfect tool, but a great place to start in weighing the stuff that needs to be/has been done plus a

Check out the 'founder's pie' calculator (google it) not a perfect tool, but a great place to start in weighing the stuff that needs to be/has been done plus a way to view, categorically, what each person brings to the table - and if you haven't already locked in ownership equity you may want to consider a performance based profit equity that leads to the promise of ownership once he's willing to commit full time to the project. Good luck!