Air barrier moisture barrier ? Faced vs unfaced insulation ?
I'd bet "probably not" on the vapor barrier, but if you have a lot of humidity, them maybe so; buildingscience.com has maps that indicate whether one is advised or not, and if so, where in the exterior wall. In most places, not. In very cold (N Canada, Interior AK and north), perhaps. In some hot humid places, perhaps. Air seal for sure. As for insulation, get something better than fiberglass batts; they pretty much suck. Roxul is better. Between the floor/ceiling of the apartments, you could insulate for noise reduction using unfaced batts (cotton, cellulose, or wool I believe are more dense than fg and there let less noise through. Besides, they don't put itchy crap in your eyes. Search here for topics on noise reduction.)