When they said "take this extra $10" EXTRA is not considered paying in advance...it's EXTRA just like they said.

If I were you, i would just in General ask for a written contract that ststes hiw much & when you will be paid since this is an evry sunday thing.

I was fill in organist when our organist was away. Payment came out of tbe church treasury & our treasurer didnt always have checks with her. I would get paid whenever. For me it was no big deal because I didnt do it but 3-4 times a year. If you are doi g it every week & they said how much they are paying you, its best to have the details in writing just for your own knowledge of how their payment system works. Some churches pay once a month. Best to not guess.