Some people are attracted to people who are older than them. Some people are attracted to people who are heavier than our culture's ideal. Some people are attracted to other people's spirits and personalities, with their physical bodies entering relatively little into it. This guy could be any of these. Unless his plan is to crash at your place and then steal your stuff in the night, or con you with a story of woe and take your cash, I can't imagine what an alternative motive from him might be. I mean, it's not like you're a rich heiress he can bilk. I would just go with it, while staying in touch with your intuition to see if anything seems shady.
As for STI's, someone down the street can lie to you about their safer sex practices just as easily as someone halfway across the world. It comes down to a couple of old adages. Trust but verify -- it's perfectly ok to ask him to get tested in NYC with you. And hope for the best but prepare for the worst -- insist on barriers.
Certainly I would say it's fine to expect him to wait until you're completely comfortable... that should *always* be the standard, right? Plus, it's not like he's coming to NYC just to visit you, he'd be coming there anyway, you're just a bonus. And anticipation makes the prize sweeter, yes?