Hi,
1. There are several possible reasons: He is: extremely bussy, not very serious, not interesting, hides something (has another g.f, married....), prefers to spend his free time doing something else (hobby, reading....)No offence, please, but that's a bad sign.
2. He might be telling the truth (they are living together because it suits them both) or he is simply lieing to you ! (want's to be "nice" to you or not hurt you).
Best regards,