Does a comma have to be used before 'because'?

Question

I have a big house because my parents are rich.
I have a big house, because my parents are rich.

Are there are some exceptions as well?

Answer 1

In this case, a comma isn't needed, but there are cases where the comma is needed. One such incident is taken from the Chicago Manual of Style:

He didn’t run, because he was afraid.

He didn’t run because he was afraid.

The author explained that, without the comma, as in the second sentence, It could mean two things:

He didn't run, for the reason that he was afraid
or
He ran, but not for the reason of being afraid.

In this case, it would be helpful to have a comma to clarify matters.

Otherwise, a comma before 'because' is usually not needed.