"Young daughter" could be in her 20's-40's and daddy could be paying her pretty well.
I think neither party should 'assume' anything but that is nice that he has someone already handling the similar job who would have insights into time management, what to expect, etc..
Ask for clarification of duties and compensation.
You'd probably be contract employee....I'm not even sure how that works between US and Germany tax wise. I bet you've got a page of questions started.