I'd just be real carefull and spell out when you have use of the facility and allow for rehearsal space when you don't have access to it.     You may even want to somehow account for set construction and put in time.   And get yourself a bulldog of a lawyer that'll put your interests first.   And I can't stress this enough: be willing to walk away.   Not needing something is the strongest position you can put yourself in and at least have the perception that they need you more than you need them.   I know that sounds rather adversarial but I think when you start something like this you have to be protective of yourself before you can be collaborative.