Continuity mistake: The Myers' house in this film is a different house than the house in part one.
Suggested correction: The house could have been remodeled.
It is implied that the house was unoccupied since the murder. So why would anyone want to remodel a Cape Cod style house that was in the first one into the huge house in this film? If you look at the interior, the house was definitely worse for wear, so it being remodeled is highly unlikely.