Looking at it in the classic sense, it's pretty much a compliment. The classic sense has an underlying wish, that the "girl next door" is pretty or sexy ...or in some fashion desirable. I suppose that could go for both genders.
I fluff my hair and say " Why thank you" in a coy way
IT WOULD DEPEND ON WHERE THEY GREW UP. If they grew up in the ghetto, I don't think I'd like it.
depends on who lives next door
It's not a bad thing to be called I guess, though not my first pick either. It means you're decent and fun; not the wild sort, maybe even shy and quiet and not too adventurious. Possibly a virgin. I'd just say thanks.
I probably would not know-I fantasize about being the dude next door.
I'd laugh. They obviously wouldn't know me very well.
I'd say "Sweetheart... You got some freaky Neighbors!"