That video is lucky. The person got really lucky :/
You need to be prepared for a lot of fighting. Have aquarium salt, and epsom salt on hand, as well as some type of QT container. Once hierachy is created (which can take weeks to create!) fighting will be rare, but CAN AND WILL still happen.
Do A LOT of research before starting your sorority.
Will you have space to put any girls that don't work out in the sorority?
If the females are sisters, there is less chance of fighting.
You need to HEAVILY PLANT THE TANK. I repeat, HEAVILY PLANT THE TANK. They need places to hide, and get away from any fighting.
Here is my tank (since then I've added even MORE plants): http://www.youtube.com/watch?v=inL2VvQb-yw
Do you have experience with bettas before this? Sororities are not for beginners. I suggest owning a single betta for at least a few months before even considering a sorority. :/