Turning down a job goes against human nature but often is the wisest thing to do.

A very large and successful mechanical contractor once told me that the key to success in his business was knowing which jobs to turn down. Everyone who's been around the construction industry for a few years has heard horror stories about jobs gone sour. Some of you probably have tales of your own along those lines. I know of formerly successful contractors who went bankrupt because of a single ill-considered project. Extended litigation from jobs gone bad have cost many contractors a ton of money, along with health problems and shortened life spans.