You did not say where you live, so Iu2019ll answer as if you lived within NYC. The answer is u201cNo!u201d.First, if you are paying market rate and you are otherwise good tenants and you pay your rent on time, the landlord would have very little to zero incentive to want to get rid of you.If youu2019re not good tenants, you cause problems, and you donu2019t pay your rent on time every month, then the landlord will want to get rid of you, regardless of the u201cillegalu201d boyfriend.So the landlord u201ccaughtu201d you, put you on notice, and you cured the problem. Problem over. The landlord cannot punish you as if you were errant children in need of a spanking.Making up some arbitrary, one-sided u2018fineu2022 or higher rent is not legal if itu2019s not in the lease, and I assume it isnu2019t since I have never seen such a clause.So donu2019t sweat it. Get back to being a good, honest, rent-paying tenant and donu2019t let the landlord make up illegal threats that have no basis in the lease.