house sitter vs custodian

house sitter and custodian both are nouns.

Word	Noun	Adjective	Verb	Adverb
house sitter	Yes	No	No	No
custodian	Yes	No	No	No

As nouns, custodian is a hypernym of house sitter; that is, custodian is a word with a broader meaning than house sitter:

house sitter: a custodian who lives in and cares for a house while the regular occupant is away (usually without an exchange of money)
custodian: one having charge of buildings or grounds or animals

Other hypernyms of house sitter include keeper, steward.

house sitter (noun)	custodian (noun)
a custodian who lives in and cares for a house while the regular occupant is away (usually without an exchange of money)	one having charge of buildings or grounds or animals