The pricing table on the Power BI website does a good job at explaining when a free account is acceptable and when a pro account is required. However, it does not explain all nor is really clear (in my opinion). So, after some digging I came up with this: an step-wise wizard that helps you determine if you can use a free account for Power BI or if you need pro (below); simply answer a series of Yes/No questions and you will know if you can use free or really need pro. Please note that this is no official communication and by no means I am responsible for any errors. Use this at your own risk.
Enjoy!