Mother In Law

So me and bf are looking for a house, we live separately. He’s very, very close to his mother and so far I’ve never had any issues with her. Now, recently he brought up the idea of us getting a back house as well for his mother to stay with us.

I personally don’t mind BUT I’m so scared that will create problems, I’ve heard nothing but bad stories with family members staying with couples.

She’s single, and a part of me doesn’t mind at all but the other half wants us to be alone.

He said he’s always going to want his mother close by

Ladies- what are your thoughts?