I do this all the time in my consulting business (starting work prior to receiving a contract). If I waited for a contract all the time, I would frequently have to do the kind of rush job that would injure my reputation.
I would say that less than 5% of the time I have found my self in the position of doing some work that I didn't get paid for. There has been only one time where the work was so specialized that it did not help in some subsequent project.
It all depends on the level of trust that you have in the people that promised a contract. If you trust them, just make sure you don't get into a time jam. Bureaucracies can sometimes take an incredible amount of time to get the simplest piece of paper approved.
That is exactly what I am concerned about. I guess they need to trust me as well that I will do the work in a timely manner as I said I would. I don't want to disappoint them especially because I also am designing a second course and hopefully teaching the courses later. I need to look at it from the bigger picture and be patient.
Thanks for sharing your experience. This is all new to me.