I first had my frame setup in a small office at 10'. I only quilted from the front at that time so it was only 8" or so away from the back wall and flush up against the wall on the right with about 3' open area on the front & left sides.
In a perfect world, you would want 3' all the way around but I couldn't wait for perfect--LOL!
I have also had my frame set diagonally out from a corner when I moved it into a room that all ready had a bunch of stuff taking up space so even in a small room, setting it up diagonally will give you the needed space front & back if you plan to work on both sides of it. I still don't use the back side of mine often enough for it to be a concern for me even though I now have mine setup with room all around it.