Doing it for nothing is something I won't do.
You are performing on someone else's property and if you aren't charging for it and it is not disclosed in a proposal, bid or estimate, you are liable for any and all damages that result.
Hourly rates are for employee's and lawyers. Even plumbers and electricians don't give hourly anymore. They charge by the service.
We don't give out an 'hourly' rate either. Due to the varying factors many projects will have, there is no way to really put an hourly rate on it considering there is so much more that go into costs.
Rod