Hi Lisa,
We had a similar situation a few weeks ago, where a regular domestic custy asked us to look after her holiday let in Sandbanks, Poole.
It's a changeover once a week (sometimes once a fortnight). When pricing, we considered the location of the place (as Sandbanks is sometimes a pain to get to at the weekend) as well as the work/time constraints.
We ended up charging our regular hourly rate + 50% which she was happy with. Upon reviewing it, there's not a great deal of work and she has regular customers each year, all of which are respectable & elderly and therefore unlikely to have wild parties!
I agree it's a difficult one and we, maybe, were helped by already having a relationship with our customer so we knew what would/would not be acceptable.