I agree that you would need at least 7' front to back, and additional room on one side to walk around. As far as the frame width, I would get the widest one your space can accommodate. Remember to add an additional 3 feet or so to the width so you have room to walk around to the back. The sled the machine sits on takes up some room, so when it's moved to the extreme right or left, you will loose at least 6-8 inches on each side, possibly more. SO a 96" frame will accommodate a narrower quilt width, possibly 80" or less. It does depend on the type of quilting you do. If you do mostly twins and throws, then it might be OK. You can always long arm the quilt in sections and join after using a QAYG technique. Not the most convenient, but it can be done.
My machine is located in the basement. Have overhead lights installed prior to delivery, and make sure there are multiple outlets available. I would set the lights up so that you can either dim them or be able to turn some off rather than all off or all on. Sometimes you need light coming from the side rather than above. The concrete floor makes it easy to get the machine level, but it is really hard on you! Remember, you will be quilting for hours. I have one of those cushion mats that fit together like puzzle pieces. On top of that I have a gel mat and wear Crocs, hot pink of course, and take frequent breaks.
Do lots of research. It's a big purchase.