> Be warned, this post is spot on if you always want to earn the same amount of money but you will never grow a company with this billing method.

OTOH, if you want to do fixed bids, you better have a really good idea of exactly how much time it's going to take you. This means that you should concentrate on doing only things you've already done, or that are very similar to them. Otherwise you'll run into something you didn't even know you didn't know and blow your estimate and eat the losses yourself.