WordNet records no synonym and no antonym for caretaker. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a custodian who is hired to take care of something (property or a person)
an official who performs the duties of an office temporarily
“he acted as a caretaker until a new president could be elected”
Synonyms, antonyms and the broader and narrower relations for caretaker come from Princeton University’s WordNet. Full sources and licences.