Several in my opinion to better track what expenses you are incurring (salary, depreciation, consulting, meals, utilities, rent, travel, etc). Generally create as many as you need to understand what expenses you are incurring and be able to trend/analyze spends appropriately. Just list out all the types of expenses you will need and set up accounts for each. Some you may need sub accounts for - an example is to capture expenses by location if you have multiple offices. I would start by looking on the web for articles about sample charts of expenses and use as a guide.