Unfortunately, the rules that everyone has talked about is the way it is in Texas. Also, don't rush off too quick to add on to your house b/c then city ordinances play into as well. You cannot have an entrance to your house through the kitchen and there are some other rules as well. Plus some cities say that you cannot have any type of commercial business in a residentially zoned area anyway.
Best thing to do? Keep doing it illegally, don't advertise and hope you don't get caught, or find a kitchen to rent