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In order to pursue him for negligence, you would have to prove he misrepresented this to you and it was NOT specified in the contract of lease. The reason for this is because the MA courts do consider that when a person has signed a written contract they have actually read that contract and understood the contract and agreed to those terms. Thus, since it is in the contract the court would hold you to have read that and under the Parol Evidence Rule, one cannot try to introduce oral statements that purport to change the terms of the written lease. Thus, he could not change the terms of the lease.
Now, you do have a chance here under MA's very friendly consumer protection law, Section 93A by proving this was an unfair and deceptive practice by the agent in telling you that it was permissible to rent to roommates in violation of the lease and you relying on his expertise in the matter since he was the one who provided you the lease. You need to start by sending him a letter, which is required under Section 93A, and you need to specify that the letter is notice of his unfair and deceptive practice under MA General Law Section 93A in that he intentionally misrepresented and allowed you to get roommates in violation of the law and the lease and you relied on his expertise when asking his advice. You can seek reasonable damages from him in your letter, such as the cost of move and maybe the last month's rent, but tell him if he refuses then Section 93A allows you to sue for triple damages plus attorney's fees and you will do so.
This is your recourse in this matter.
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