The description for the main area is pretty straight-forward, if not a little more posh than what Sector would normally spring for in a safehouse for one of their cells -- that, however, is because the area was already in place for some time before Sector got Tifa's permission to utilize the location for a new cell's base of operations.
If you're wanting dimensions: the safehouse layout is pretty much square, bisected diagonally through the middle by the hallway (to the half-way point of the diagonal, where the opposing doors are). The half that you're in right now is the living area, where your personal quarters will be (they won't be grandiose, but it's pretty decent for living quarters). The other half is the shop area, where your ground transport will be located, as well as a work area for R.C.'s demolitions work, Cayla's tech support, etc.
If you want specific dimensions, I can try coming up with something over the next day or so. Needless to say, though, you've got some pretty decent space, all things considered.