Crenshaw by Catherine Applegate

This is a touching story about ten year old Jackson and his imaginary friend, Crenshaw, a very large cat who likes to skateboard, take bubble baths, and stand on his head.  Jackson is a smart boy, who is concerned about his family's finances since they are often hungry and are preparing to sell off most of their belongings to try to pay the rent.  His parents try to hide the situation from Jackson and his five year old sister, but Jackson remembers when they lived in their van a few years earlier and he does not want to do that again.  He knows that he is too old for imaginary friends and thinks he may be going insane when Crenshaw returns, but he learns that imaginary friends are always waiting to help children through difficult times.