Good luck and keep us posted!
You need to look at all aspects of the business. How many employees, cost of insurance, workman's comp, taxes, rent utilities, tools, location, type of work you will be doing. Are you going to specialize or do general repairs and maintenance? Are you going to sell and buy car parts? You really need ashop software to help with invoicing and record keeping. You also will at least need enough money to live on for about a year. These are just for starters. You will notice other things you need daily.