How big is the house?

Answer 1

a mansion is 5,500 sq feet or bigger to be considered a mansion

Another answer:

How big does a house have to be to be a Mansion ?

Answers vary.

Some people say the limit is 5,500 sq feet or greater.

Some people say the limit is 7,000 sq feet.

Some people say the limit is 8,000 sq feet. This answer also mentions that a mansion is typically three levels tall and must have several rooms on each level.