I encountered a landlord asking for a $60 fee or deposit on top of first month's rent, last month's rent, and security deposit (equal to one month's rent). This is illegal, since MGL c. 186, §15B only provides for key/lock replacement costs on top of those payments (and this is unrelated to keys and locks.)
Since I haven't yet entered into a relationship with the landlord, I'm guessing I can't sue for damages. If I did pay, I suppose I could legally subtract $60 from my next month's rent check, and the landlord would then be unable to successfully recover it. (I wouldn't want to live in an adversarial situation like that, of course.) Are there any other mechanisms for enforcement?
As a general note... no, I wouldn't want to live with a landlord in an adversarial relationship, but I'm privileged to have a wide range of choices of where to live. Not everyone is so lucky.
Employment / Labor Attorney
If you paid, you could demand it back. If the LL didn't return it then you could sue, and win--I have a case almost exactly like that right now.
In theory, you could also refuse to pay it and then, if the LL didn't agree to lease the apartment, you could also sue.
You could also report the LL to the attorney general's housing division.
In the end, though: are you sure that you want to get into this fight?
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