I have a minimum order $. I don't care if the person wants a cupcake if they are willing to pay I am willing to make it.
Just make sure your minimum amount covers your time. It takes me just as long to mix, bake, clean up, make filling, make icing, fill and ice a 6" as it does a 10" (okay, baking a 10" takes 20 minutes longer - close enought). So I want that 6" cake to pay as well as a 10" cake because my time invested is the same for the basic work (decorations aside).