You shouldn't be living with your ex.
Shane is living in a shared apartment with a girl that he used to date who doesn't have much respect for him.
Shane wants to save money on rent.
Shane evicts his ex and finds a new roommate to share the place with.
Shane continues to stay with his ex because he only has to pay half the rent.
Shane's ex learns that not everyone will tolerate this sort of treatment.
Shane's ex thinks that he is a pushover and treats him poorly.