John 14:2 (KJV) In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you.
Are “mansions” large, impressive houses, or are they something else, such as resting places?
I think mansion is the KJV translation of something like Dwelling Place. I have read that at that time rooms were added to
a Parental home when a Son was married. I think the idea is that the Church is the Bride of Christ and this was his way of explaining. Still I wouldn't refuse a mansion if offered one.