Need advice

So my boyfriend told me yesterday well he asked what I would think if him and his ex became roomates. I told him I wasn't up for it. He said he can't stand living with his grandparents anymore because of the condition of their house and his grandpa won't do anything about it and he can't afford a place on his own. I won't be able to afford a place for about a year. He said it's not for sure yet of they will room together. I made it clear though that I didn't want him to. I said will I be able to stay with you anymore and he said yeah I don't care what she says you can stay whenever you want. He also told me he wouldn't sign the lease so if he wanted I move he could. I able died him what of she tris to make a move and he said if she did than he would leave. Idk I do trust him it's her I don't trust. Any advice or thoughts?