This one is easy Roslyn. The NEC mandates in 230.70 (A)(1) that "The service disconnecting means shall be installed at a readily accesible location either outside of a building or structure or inside the nearest the point of entrance of the service conductors."
This clearly allows the service entrance conductors to enter the building for a short distance to get to the disconnecting means.
There is no set NEC numerical limit but it is pretty clear that you are limited to a minimal distance.
