Awesome.
The two things you will want to look into first are getting a tax ID for your business so you can do your books up right, and I think you can just go talk to the town clerk about that. At least he will point you in the right direction.
The other one is you will need insurance in case of any mishaps. I can't imagine that insuring a power washing business with only one employee would cost too much. You could call an insurance company for a quote.