If you are working at home, don't require a professional license, and have no employees, the easiest/cheapest is to just be a sole proprietor. You will need to register an assumed name (see the website for your state on "Doing Business" and it will explain how to do everything.). You have a low-liability business so you don't need the corporate protection.
You will need to fill out a detailed personal tax return in order to claim your office and other deductions. That means you have to use the office SOLELY as an office - no beds or gym equip can be in there. You will need to use an accounting software program like Quick Books to track everything and make invoices. You are in a high-profit business - you will need deductions BADLY as you don't have any expenses other than software and paper. You should consult a small business tax advisor - the Quick Books website has links to Q-books accountants in your area. If you both use the same books, then it is easier to work together.
After the first year, consult the advisor about an s-corporation as the tax benefits are better. The Q-books advisor can explain all that too. In otherwords, get advise from a professional as to your specific circumstances. The small consultation fees will be worth the tax savings.
You are very fortunate and have a good business niche - be smart and do it right and it will reward you!!