Nail your "scope of work" down, and stick to it. When things get outside the scope, that's an "extra". I'm used to commercial work, and it is a little different than residential. I should offer my excel spreadsheet again. It's good for commercial jobs, and I suppose that it would be good for residential. So, again, for all who have microsoft excel, and want the spreadsheet, send me an e-mail, and I will send you a "blank" and a sample estimate. It may take a day, or so, but I will get it to you.
The Watt Doctor