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?
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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
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.