How does a residential/commercial handicap spot work?

Ever seen a time restriction on a disabled spot??? Yeah...me neither.

You cannot use it at any time. It must be empty whenever no one handicapped is using it.

In San Francisco it makes no difference what time it is. And the fine is now $825.

You say you were required to have the spot. What specific law or regulation requires the spot and what does it say?

I don't know how your local government is structured, but I might be tempted to write a letter to the possible applicable authorities and ask for clarification. Possible recipients might be your city council representative, the transportation department, the police department, city office that handles issues pertaining to minorities such as seniors, disabled people, etc. (in my city that's called the Office of Civil Rights), etc. Make noise in writing. You'll get an answer (in writing) which may come in handy if you ever DO get a ticket.

You can get a ticket if you park a non-handicapped placquered vehicle in a handicapped spot. But who is going to ticket you? Do the cops patrol your parking lot?

That said, if the business is closed at night, and you ave more than 1 spot, why do you have to park in the handicapped spot? It is just one spot.