This business is like the lawn mowing business! Everyone does it!
Its a low cost start-up and everyone does it. You must put youself and your business above the rest and offer the best service possible. You do all this by experience and education. You need experience and education in marketing, office work, washing, insurance, equipment, chemicles, accesories, and when to use them and not to use them. I know there must be much more information before you need to get started, but Larry is right if you do not do you home work and educate yourself the correct way you will be out of business in 18 months. You will have blemished your name and the trade.
Please think much more beyond the $500 pressure washer in the back of the pick-up type operation, because it will not last long. If this is your passion and long life career goals then you must do it. If this is something that you been thinking about because you seen another person doing it, well........
it might not be the best move. You must follow your passion in order to make the best career for yourself.