Recently, I was building a house and had just finished installing the drywall. The drywall contractor was to provide materials and labor for a turn-key result. The job was done well, and the bill arrived at my office.

The bill included an extra $350 charge to "account for an increase in drywall material costs". I assumed that this was what we had originally agreed to, and I went ahead and paid the drywall contractor the amount on the invoice.

After the check was in the mail, it occurred to me that I should confirm that this $350 obligation for material cost increases was actually mine. It was not. I had assumed incorrectly.

When I tried to get the $350 returned, I was given the run-around about how the amounts were already processed, and there was no way to return the sum. I didn't have time to sue in small claims court, so I let it go and learned my expensive lesson: once the contractor has your money, you have very little leverage. Always be sure to compare the invoice with the original proposal and try to remember to negotiate potential price increases up front.

Former builder and instructor of "Save Time and Money in Home Remodeling" cont. ed. course at Emory University