Necessary Agreement for running a bar

[Martingale Kim]

Not sure if this is the nest place to post, but I'm about to take a partnership with a friend who has an established restaurant business , he has a bar on premise but the bar has been obsolete and does not generate enough income from the bar, the dinning portion is fine.

For the partnership , I don't need to contribute any capital but will take a share of net profit from the bar only, in return for my marketing and management of the bar.Since no capital or expenditure is needed  from me, what kind of document is needed to safe guard my interest here.