The first apartment.
From Create Your Own Story
You hurry towards the first apartment. Looks like the best sniping tower you could possibly find. You don't know where to hide, though. You want to snipe from somewhere upstairs, but you don't know which area to pick.
To the roof. (Little areas for cover, but few people suspect you'd be sniping from the roof.)
Fifth floor. (Plenty of cover, but you'll be easy to spot, having to lean out of the window.)