I'm pretty sure this is a one-shot, but I could be wrong. I think it starts with Puck finally packing up his stuff and leaving Lima, long after high school, and moving to NYC. He ends up getting a job in a music store and running into Rachel. Since he doesn't have a permanent place to live, and she's kinda lonely, she invites him to stay with her. It starts as a roommate situation but turns into more. I do remember that the story also has a count of the days that go by between the time he moves in with her and when they finally get their happily ever after.
Like I said, I think it's a one shot, but I could be wrong. It could also be that this is all a part of a bigger story and I just can't remember that..
Thanks in advance!
(Mods: I think I got all the tags right, sorry if I left anything out..)