I am thinking about holding cake decorating classes in my home.. Kind of like a crash course in it.. has anyone ever done that before? If so, where do I start??

Find out if you are zoned for it (probably if it is a small town), get all the licenses you need. Make sure you have all the tools and ingredients that everybody will require (unless you tell them to bring: (enumerate what), copies of the recipe, etc. Advertise, answer the phone, greet, collect funds, teach, enjoy the fruits of your labor! I know it sounds that I am not being serious but it depends on your town. So the first call would be to call the Municipal Office and they will tell you what the next steps are. Good Luck!