Where to start your business?
ITIL book
After choosing a business idea, you need to figure everything out in numbers, decide on expenses and income, and with detailing to a penny.
If errors are found at the planning stage, then the model will need to be adjusted. This can happen if a competitor's supplier provides goods at better prices. At the planning stage, it is required to do everything in order for the business to be profitable. Draw drawings and diagrams with explanations. This is your instruction, following which the chances of success will increase.