For part-timers I have a 3 day/week minimum and charge a higher fee because they can schedule around stat days. However, once your calendar is marked for every Tues, Wed, Thurs make sure they know those days are payable every single week no matter if they miss a day for any reason, including sickness. I think July 1st is the only day that might fall on a different day besides Monday, so make sure they know that will be payable if it falls on one of their days. In other words, no matter what happens they are paying for 3 days/week.