As a Teacher, I offer several options:
I have 3 rules for all my teaching events:
1.) Respect the time of myself and others. Arrive on time, call ahead if you'll be late. When arriving late, enter quietly and try to make as little disruption as possible.
2.) Respect the space. Whether in my home or any other location, remain only in the designated area (with access to bathrooms, obviously). Snooping, stealing, being loud or obnoxious, or any other such nonsense warrants removal from the teaching event without refund.
3.) Respect the value of the teaching event by paying in full either prior to the event. Preregistration is required most of the time, same-day registration may or may not be allowed, depending on material availablity and space.