Why does Scrooge live in a big houes on his own?

Answer 1

It was originally Jacobs home but Scrooge took it after his death. No one wanted to be with Scrooge and he lived a miserly life with no one to think of or care for him. He had driven people away from him that tried to care for him. However the house was turned in to offices which Scrooge rented out keeping only an apartment for himself.

Answer 2

Scrooge lives in a big house on his own because he is a wealthy and miserly man who prefers solitude and values his privacy. His wealth allows him to live luxuriously without the need for companionship or sharing his space with others.