Make sure that you have enough cubic volume to split the room into 3 rooms that are big enough to sound good. If not, it's better to have one all-purpose room big enough for good sound, than 3 rooms, each too small to sound good. Generally a volume of 2500
cubic feet is a good rule of thumb.
For more detail on why, like Glenn, I am suspicious of small booths, see RealTraps - Vocal Booths