Estimate the monthly costs of living your life. Be sure to include monthly allocations for expenses that you pay less frequently (e.g. car registration). If you are working out of your home, you may share the cost of some expenses with your business. Making an accurate allocation is important when you file your taxes. For the purpose of this exercise, inclusion somewhere is more important than the proper allocation between living and business expense. Be careful not to double count expenses.
This is the minimum amount you will need in "salary" from your business.