Erik really enjoys little moments like these, however mundane the situation; for someone with significant control issues, it's nice to be asked by the resident telepath. It's not that he doesn't trust Charles—as much as he can trust anyone—but he cannot forget the man's abilities, no matter how comfortable they may become with each other's company.
(In any case, it's nice to surprise a person now and then, telepath or otherwise.)

"I've taken care of it." Funny how he can make subletting sound like a mob hit. "Go on, go look—there's a sun room in the back. And you'll want to see the second floor." The not-quite-an-attic, he means, accessible by a narrow staircase that doubles back halfway up on account of the limited space.