Answer:
good neighbor, predicate noun
Step-by-step explanation:
In the question, good neighbor is a predicate noun because it comes after the linking verb "is" and re-identifies or renames or the subject which is Mr. Brown.
For a clearer understanding, predicate nouns also known as predicate nominative are nouns (like "good" which represent quality) that come immediately after a linking verb (like "is") and re identify or renames (good neighbour) the subject of the sentence (Mr. Brown).