I've never raised pigs for others but have cattle and chicken. You mentioned selling sausage. I would check with your local ag officer to see what the rules are for selling processed meats in your state. I know when I lived in TN, I had to have anything that was processed done in a USDA facility to legally sell it. Even my whole chickens had to be processed at a USDA facility, stored separately from my personal freezer items and my farm was inspected by a USDA inspector. Selling a side of beef or live chickens that the customer processed themselves was OK and didn't require any special permits.