For someone sharing an apartment with a non-Jew, do the common doors in the apartment need a mezuzah? Does the Jewish person's bedroom even need one if the apartment is shared with a non-Jew?
When a Jew and non-Jew share a house, each having his own designated room or area, then a mezuzah is not posted on the common doorway. (Rama Y.D. 286:1 with Pitchei Teshuva 3)