"To pay" someone is to give them money. "To be paid" is to receive the money. If you write: "Money will be paid by you..." then you are the one paying/losing/giving away money. If you will be paid on the last Friday of each MONTH, you will RECEIVE payment on that day. You will get money. You won't be giving any of it away...hopefully.

"Money will be paid by you on the last Friday" The only way that phrase could work is: "Money will be paid TO you"

MONTH......not mouth