The Departments of Justice and Housing and Urban Development have very helpful memos on accommodations (changes in policy) or modifications (structural changes). These memos can be found here: 

Reasonable Modifications 

Assistance Animals

Let the owner know that you cannot do that because it violates the law! A person who has a voucher is a member of a protected class – it is illegal to publish discriminatory language targeting a member of a protected class. There are no exemptions to this rule.

Fix the issues! This isn’t just a fair housing issue, it’s a state sanitary code issue. Mass.gov has resources about habitability rights and the standards of fitness for human habitation.