Rewrite the sentence by making the pronoun agree with the antecedent.
every good homeowner plays their part in keeping the neighborhood clean and safe.

Every good homeowner plays their part in keeping the neighborhood clean and safe.
Antecedent: every good homeowner
Pronoun: their (which is incorrect because "every homeowner" is singular)

For singular antecedents, we should use singular pronouns. Singular pronouns include: I, he, she, it, and you. Since this refers to a second person (every homeowner), we can't use "I", "it", and "you". Hence, we can use "he" or "she" instead.

CORRECT SENTENCE: Every good homeowner plays his/her part in keeping the neighborhood clean and safe.