What are your costs for the cake? How long will it take you to make? How much do you want to make per hour?
Costs are not just flour, sugar, eggss...
All ingredients (even if you already have the flour - it costs x amount per cup to replace)
Gas to drive to purchase ingredients/supplies
Cardboard cake board
Water for the dishes
Electric/Gas for the oven
Soap for the dishes
Insurance (car and business)