It seems to me that there were 2 areas that needed to be improved. First, the client should have had a detailed bid detailing exactly what needed to be done, and what he was to pay. That way there is no room for misunderstanding when it is time to write the check. Second, I think you needed to have a better understanding of what your costs were, and the time you would need to complete the job. I think you came out ahead, because the rental company refunded all your money. Those guys never treat me that good. I think all in all it was a good experience for you.
Nothing teaches you how to bid like working for the "crack head" price!!!