What made Sherlock immediately accept John?

 (Sherlock Meta by Ivy Blossom)

mediumaevum asked:

Something's bugging me and I can't find "official" fan statements about it, so I thought I could ask you, if you don't mind. What made Sherlock immediately accept John? Back in Bart's, he knew Mike didn't have a phone, and John did. He asked him straight on about the violin and other stuff. What was is it he deduced about John that told him "he's the one"? Thanks!

Ivy Blossom:

At what point did Sherlock decide that John would be a acceptable flatmate? That was when he deduced that Mike Stamford was bringing him a potential one who had plenty of good reasons for needing a flatmate himself. Sherlock’s deductions (no strong ties, soldier, doctor, freshly back from a war) tell him enough to go on, as he says. He wasn’t looking for someone who would be perfect. He was looking for someone who would have him.

Sherlock hadn’t asked, “Who can I stand to share a flat with? Who will help me? Who will make my life better? Who will become my one and only friend?” He asked, “Who would have me for a flatmate?” Sherlock decides in that moment that John is alone enough, desperate enough, and possibly strong-stomached enough to be his flatmate.

He clearly has no clue who he’s just met. He has no idea at all how John is going to become central to his work and his life. He’s only solving an immediate problem. It’s less “he’s the one,” and more “this one is not going to say no if I offer him the second bedroom.” He’s so confident about it that he immediately moves in himself.

Though I suspect he also thinks John is kinda hot, because he’s flustered the next day when John drops by. We all know about Sherlock’s thing for soldiers. But that’s another story.