I am property manager and ask me anything about rent control, maintenance, noisy (or nosy) neighbors, subletting . . . shoot.
Would you be willing to accept rent a week "late", if you knew that four people with very low income were renting the place, and one of them didn't get paid until later? That's currently happening with a friend of mine... he's so strapped for cash, that he's unable to pay rent till the second week, when he gets his pay check. He's asked for an exception, showing proof he didn't get paid till the second week, but they refuse to make an exception, and he ends up losing $50 a month on late fees.
My upstairs neighbours are brutally noisy - screaming at each other. Realistically, what recourse do I have, if any? Currently I just keep reminding myself that this is temporary, soon enough I'll have my own house a million miles away from these idiots.
I am not on the rent collection side of our organization but can answer your question with some caveats. First, I am not sure if your friend resides in America or Canada. Landlord/tenant laws will vary by state (or province), municipality, and certainly by country. That said, a property manager doesn't care if you have to eat your own toenails to make the rent. You've signed a lease for a certain duration with a specified rent amount. Think of the late fee as a type of compromise between the property owner and resident. It is expensive to evict someone as it involves filing for it in court, hiring an attorney, and money lost from the rent that is not collected over the course of the eviction. In L.A. it can run into the $5,000-10,000 range in lost revenue, legal fees, and the cost of flipping a unit once the resident has been evicted. Not an envious process. On the flipside, once you are evicted a negative mark goes on your credit history which will boost the cost of renting another apartment into the stratosphere. Our company won't rent to someone who's been evicted regardless of what they're willing pay as a deposit. I would tell your friend to either A. find cheaper living arrangements or B. a better paying or second job. Either way paying the fine is better than having an eviction on your credit history.
Look at your lease to see if it mentions anything about a noise policy (e.g. "Quiet hours are between 9 p.m. and 7 a.m."). If so make a personal or anonymous complaint to the landlord about the noise levels in the adjacent unit. Remember that your lease is a legal document, so the standards set therein must be enforced by the owner/property manager. If their fights escalate to the use of physicality then it becomes police matter. Call the police and report it as domestic violence. Years ago I did that to a set of neighbors and even lied about one hitting the other. They were both carted off to jail and evicted within a month. I felt nothing about it and still don't.