Ok, what I have in mind is a 18 year old guy, who has a crush on his next door neighbor. He is rather naive and inexperienced. Not to mention never expecting to get the girl of his dreams, who happens to live next door.
Now there are a couple ways I see this working out.
Either they have been friends since they were little, and something just sorta sparks.
One of them just moved in.
She is more popular and somehow they ended up having to talk and spend a little time together.
Or, they both have feelings for each other, and were both oblivious to the others shared feelings.