Social and environmental impact is not monopolized by a company’s CSR team, you can make an impact from any role within any company. Showing off your intrapreneurial skills is a much stronger approach to getting hired in a CSR job and one that can be achieved from either the for profit or the nonprofit career field.
The truth is, there is no defined correct order for how to start a career in CSR, you can start your career in a nonprofit job or in the for profit field, or transition between them. Often a combination of both fields will give you a more diverse set of skills.
Ask yourself two questions: what are you good at and what does impact means to you? This will help you discover where you can have the biggest impact.