What's a hotel though? Where I'm from, running a bed and breakfast (defined as 4 or fewer rooms and 8 or fewer guests) doesn't require any kind of special licensing.
Of course running it out of an apartment runs afoul of every rental agreement I've seen.
A common zoning distinction is that a bed & breakfast is a private home where the host lives in the home. If the host does not live there, many cities/towns would then consider it a hotel and subject it to different rules.
I think a lot of the arm waving about airbnb is because of the latter situation. I don't think many people seem to have issues with renting out a spare room.
We don't have zoning in my country. I've had two companies, their address was always my apartment. I was also manager for a company - it was located in an apartment, then a house, then finally a commercial place (when we got to over 25 people).
Of course running it out of an apartment runs afoul of every rental agreement I've seen.