I have to disagree there. Remember that labor costs you money, either your own time or a hired person's. You health insurance costs or rent or whatever don't stop adding up every day just because you decided to stop charging a customer after some predetermined number of hours. And, the possibility of a big problem (on the job injury, van wreck, gashed wallpaper) is still there even if you are not charging, but you will be responsible for the costs of the mishap even so.