Minerva did seem surprised by that question, and she didn't mean to sound as if she was answering a student when she answered him, but fell short. "Of course, Mister Weasley. Professors are required to keep a residence within the castle."
As he'd stood, she stood too, and after an almost awkward moment of considering it, held out a hand to be shaken. "Paperwork will be owled to you soon, and you know when the term begins. You're welcome to take residence here as soon as you'd like, though."