I agree with Val - sounds too weird. Especially since he never even gave hint he as thinking of moving, let alone moving 4 houses down from you!

Its one thing ot meet a neighbor and start dating, another to have your date become your neighbor overnight.

Keep an eye out for him and watch for all the little tell-tale signals you might have missed before - is he polite always, or more so in public? Does a little aciton or word change his whole mood in a flash? Can he be possesive? and so on.....

I would be concerned if I were you. Manipulative people do theses kinds of things.