"You can stay here," he tells her without realizing how strange it sounds at first bofore adding. "I mean, while you're in this world or whatever. I wouldn't want you have to go off hoping that things were similar enough to find a safe house."

It's awkward but gentle, he very clearly doesn't offer that kind of help to people often. Not only just because he doesn't really have much of anything in his apartment, but because he doesn't feel like he owes people things.

So why does he feel like he has to help Natasha?