Get It In Writing

Always get the gig details in writing.  If all parties involved are real professionals, no one should object to setting the basics of the engagement in a fixed form. 
Disputes can be avoided, details clarified, and relationships maintained by making sure that presenter and performer have the same information.  

This fixed form can be be a formal contract (I use the less intimidating term, performance agreement.) or a simple email spelling out the who, what, when, where, and HOW MUCH.   In addition to those basics, you might include things such as set up time, number of breaks, and permission to sell merchandise.

Avoid too many details.  Do not overwhelm your client with minutia.  People like simple.
I have toured for over seven weeks for a well known agency with only a ONE PAGE contract.

Bring the performance agreement to the gig.



The weakest ink is better than the strongest memory. 
Chinese proverb