“A bad neighbor is as great a pain as a good one is a profit”
πῆμα κακὸς γείτων, ὅσσον τ’ ἀγαθὸς μέγ’ ὄνειαρ·
(Not in love with the translation of ὄνειαρ. Any suggestions?)
Hesiod, Works and Days 346
ΕΥΔΟΞΑ ΑΓΝΩΣΤΑ ΚΑΤΑΓΕΛΑΣΤΑ
How about “A bad neighbor’s a disaster as much as a good one’s a boon”?