Just phone the CRA and they issue you with a business number over the phone. You don't have to set up a payroll account, except you want to. You can pay the employee from your own earnings every month or bi-weekly, provided you give her a pay stub for each payment. I think there is a free pay stub preparation software on CRA website that you can use every month. But you don't have to worry about pay stub or payroll until the employee starts working.