Starting project with Unity Free and upgrading to Unity Pro later on.

EULA says:

You May Not Use Unity Personal with Unity Pro or any Unity Pro Add-On Products You may not combine or integrate Licensee Content that you develop with Unity Personal simultaneously with any Licensee Content that you develop with Unity Pro or any Unity Pro Add-On Products. Licensee Content developed with Unity Personal will be tagged with an identifier that is used to enforce this restriction.

FAQ says:

Q.-Can I use a Unity 5 Personal and Unity 5 Professional license on the same project/computer/same studio/team?

A.-Developing commercial content using the Personal and Professional editions of the Unity editor simultaneously is not allowed.

So what happen if i start my project in Unity Free and then during development i will find out that i have to buy Unity Pro for additional features? Does that mean i can't port my Unity Free project to Unity Pro? I never developed in Unity so i don't know if Unity Free will be enough for me or not.