Well, I think the insider tips is they should tread very carefully as it's not normally with in the stage managers prevue - it involves income, ticket sales, gross and net - they will most likely need access to that . . . depending at which level and they are producing. And, some managers, agents, etc - may try to take advantage of a stage manager who negotiating these rights instead of a business manager or a general manager.
Just think, if you a had theatre company have a assistant technical director hire a PSM - that would a little odd, right?