The old fashioned way is good for starting a business. Visit local, non-franchise restaurants and grocery stores. Present them with a free pie, your prices, and minimum order. Show them pictures of your baking space, and explain the payment plans you offer. You may be able to rent a commercial kitchen space to follow health department rules, and buy a space later. You will need enough money to buy baking appliances, utensils, and ingredients for the first month. You will need a delivery vehicle, food license, and sanitation course and license. Packaging labels will need to include ingredient list, and nutrition values.
I don t believe you can patent a recipe. You can keep it secret but you can t patent it. As for writing a business plan and getting the information you need for a business, check out the SBA and/or SCORE at the website links below. They are FREE sources for help. Take action or you ll be sitting around with the hot idea until it s stone cold.