If the game is going to be for free. Forget all that mumbo jumbo stuff about protecting your assets from your own team members. Personally I was part of a project (now silently halted), and all the members were literally from different parts of the world. There was no problem with any of the people I had worked with.
You probably should to worry more about the important stuff like, are you up to the challenge, how good of a grasp of the GE do you have, how are you going to keep the entire group continuously motivated and interested, how to get people to join your team, etc.
If you’re going to sell it. That’s an entirely different story. Probably if you were to sell it, make sure you know the GE really well, therefore you don’t need a lot of help from others. Make the whole hierarchy centralized, with you possessing the entire content, while others just contribute parts of the content like characters, animations, textures, etc and you can just piece it all together. That way even if the person leaves, they’ll only have the files that they created, which they technically should have full ownership over, unless you bought it from them.