Scale of home mining and transitioning to professional

What constitutes amateur vs professional mining?

Things like hardware - scale and type, power, location. i.e. You may go from having 1 rig at home with 6 gpu to 72… Maybe installing server racks?

I know limitations for the home are power and cooling more than anything.

How much hash power would be considered “Holy F”? To a new miner 1 GH/s of ETH hashpower sounds amazing but not so much to a professional.