Is it possible to start a project in the free edition of Unity and then move into Unity Pro (when ready) to utilize all of Pro’s features?
Yes
Yes.
It doesnt break anything.
There’s nothing to move, nor is there actually a “free edition” (or “pro edition”) of Unity per se. There is only one Unity app, and free/Pro is just a license. When you buy Pro, technically nothing changes in the project and you don’t download anything extra, but instead the features which are already there are activated.
So basically yes.
–Eric
Thanks for clarifying everybody. I think Unity 3d sounds good for my project. I was deciding between Unity, UDK, and Source Engine.