"The Lodger" by Mad_Martha.
First read: 2005.
Second read: 25-11-2007.
Notes: It's interesting to read this because you can see how much the pairing has progressed and how some cliches have been lost either to canon evidence or higher ratings. That's another thing, Harry and Draco's emotional codependency is pretty clear but their romantic/sexual relationship is merely implied. Honestly, I thought PG-13 warranted at least a kiss!