Thanks in advance!

Some people thought that Isabelle Berberdown was rich because she lived in such a big house. She wasn’t, of course. The house had belonged to her grandparents, and her grandmother’s grandparents. The Berberdowns hadn’t bought the house—they had inherited it. Isabelle’s parents worried, sometimes, about finding the money to keep the house in shape, but they did their best. Still, many of the floorboards and steps creaked, and sometimes the pipes made loud groaning noises when the faucets were running.

Isabelle loved her house. She loved the rambling rooms, the wood floors, the big staircase, and the creaky back stairs. She loved hearing her mother’s stories about growing up in the house and knowing that she slept in the same bed her mother had

You might try getting rid of the wasn't and had. In adult novels, I'm told, they make the sentences too passive. I don't know if that applies to children books however.

You have the feelings there and a hint of mystery which is good. Everything pretty much is okay.