Hi Mike,
Welcome to the wonderful window cleaning industry. Good luck in your venture. My advice is only to make sure you are reliable firstly, you turn up when you say you will and your customers will stay with you forever.. The speed will come in time, don't rush things, if you miss corners or even a window and its a new customer they will always be doubtful of your work and more likely to try someone else.
GOOD LUCK !!!!!!!