You would have to check your local codes, but we have three separate service entrances (main panels).
Our electrical meter is located on a pole out at the road. Then the power comes down to a junction box behind our pump house. Separate lines then run to individual service entrances at the pump house, garage, and our house. Each building has it's own main breaker, grounding electrodes, etc. Completely seperate and isolated from each other (other than the incoming power).
We built the pump house first, then our garage, and finally the house. So we wouldn't have been able to run a subpanel off the house anyway.
However, I did run a small 30A circuit off the house panel to a small subpanel in our storage shed.