Keep a stash for Uncle Sam
Another factor that is too often forgotten is the amount of money you have to pay the tax man. Before you make the leap to full-time entrepreneur, calculate the net amount you need (after taxes) to sustain yourself and your family. Then add in all your business expenses to that amount, remembering to factor in additional self-employment taxes that you did not have to bear as somebody else's employee. The final figure is the amount of revenue your business needs to take in before you can quit your part-time job.