If it's the place I'm thinking of and the owner I'm thinking of then yes it's kosher. But the chance of you getting the whole week with friend is slim. Her flats book up quick. But try. X

These kind of flats do work out cheaper if you rent for the month but never part with a month's money to any flat. There is always the possibility of them being raided. Imagine that happening a day after you've paid. I never part with more than the equivalent of one day at a time.