@Richard385
if I understood you correctly your cleaner can only come on Saturday so you can rent to just 1 group of guests, regardless if they book just 1 night or 7 nights? And you want to charge for 1 night the same as for 7 nights?
If so then I think you have just 1 option and you should work around:
- block every Saturday (so nobody can stay/check in /check out on Saturday),
- set minimum stay to 4 nights so 2 groups of guests can't book the same week,
- set your nightly accommodation rate as low as possible (10€)
- and a cleaning fee as high as your weekly rate.
It is not ideal and it will vary depending on how many days are booked but it will be close. You will lose bookings for 1 -3 nights but it would be too expensive anyway.