These are good, but I would probably ask, Where do Mr and Mrs Brown work? and if the answer was not obvious for their job I would follow it up with: What are their jobs at that place?
Eg. If I asked: Where do Mr and Mrs Brown work?
and the answer is: At a school.
I would be safe to think they are teachers.
However if the answer was: In an office.
I would then ask what are their jobs in the office?
and the answer would then state a more specific type...filing, reception work, or whatever else.
These are my thoughts, hope they are helpful :)