housemate vs occupant

housemate and occupant both are nouns.

Word	Noun	Adjective	Verb	Adverb
housemate	Yes	No	No	No
occupant	Yes	No	No	No

As nouns, occupant is a hypernym of housemate; that is, occupant is a word with a broader meaning than housemate:

housemate: someone who resides in the same house with you
occupant: someone who lives at a particular place for a prolonged period or who was born there

Other hypernyms of housemate include occupier, resident.

housemate (noun)	occupant (noun)
someone who resides in the same house with you	someone who lives at a particular place for a prolonged period or who was born there