Underestimating startup costs.
There is nothing worse for a startup – I mean nothing worse – than beginning a new business and not having enough money to make a go of it. When you start a business, you put a lot on the line: Your name, reputation, money, other people's money (probably), your family’s future . . . and that’s just for starters. So you have to give yourself the best chance possible of making a legitimate go of it.