"Clueless Mary" Windswept@home wrote

By visual inspection, roofer diagnoses buckling in some of the plywood
sheathing and takes a down payment to buy supplies, including the
plywood sheathing.

This would concern me. He should not need money from you
to get the supplies. From everything I have read, a reputable
contracter has a line of credit with stores. I have never had to pay
for materials up front like that.

nancy