I think Monday payments work if you don't charge a security deposit.

I do hold a one week security deposit for each family so I am covered if they were to leave me high and dry at the end of a week. Hopefully I have chosen great families who would never do that though.

I actually made my payment day every Thursday. That way if a parent forgets to bring money on Thursday I still have the Friday to collect the fees rather than waiting a whole weekend. Parents seem happy with the Thursday and have hardly ever 'forgot' to bring it. It works great for me and I feel very happy going into every Friday