By law, if the cash deposits are linked to a single transaction they have to be reported no matter how you break them up. Consecutive daily cash deposits of 5k or 9k would certainly trigger a report.
I don't see what this seller is concerned about with a check for the proceeds.
I dont either but he is going to get a bank check for the boat. i would rather have it recorded by his signing the check.
I just had a thought, maybe he is getting ready to declare bankruptcy?