Right on @Darren Sager
The rental market is complex. Here are the basics:
There are 3 types of listings:
Open listings - typically from larger management companies. These listings are open to every agent in the city and can be very competitive. Your broker can get you access via a set of keys or you may have to set up an appointment with a leasing agent. These listings are considered CYOF (collect your own fee) typically. Examples: AIMCO, Rose Rentals, The Brodsky Organization
Exclusive listings - These are where the landlord signs a listing agreement with one brokerage and/or agent. The agent has the exclusive right to list and show the apartments for a specified period of time. They also set the fee for the tenants typically. If the listing agent is a REBNY member they are required to share the listing as a cobroke (more on that later) with other agents.
Pocket listings - These are sort of hybrid listings. Think of these as open listings that only a few people know about. They typically aren't well advertised (to brokers and agents) and normally only a few agents will have access to them. These types of listings can be ethically troubling though if you're a REBNY member. If you are refusing to sign an exclusive simply because you don't want to cobroke (and split your commission) then that could be an infraction of the rules set by REBNY.
REBNY (Real Estate Board of NY) is basically an ethics board that helps to level the playing field for brokers and agents in NYC. Without a governing body of some type, the competition can get too fierce and the RE sales and rentals game becomes cut throat. REBNY makes sure that people are playing nice with each other and the everyone has a fair shake.
REBNY offers the RLS (syndicated through OLR, RealtyMX, Nestio, and others) that acts as a MLS for member brokerages. Most rental listings on the RLS are exclusive listings that would be cobrokes (commission is set by the listing broker and split between listing broker and tenant's broker). Some open listings are also posted on the RLS, with varying accuracy.
Commissions: Legally speaking, there is no standard commission in any aspect of real estate. I have had deals happen for less than one month's rent all the way up to 15% and anywhere in between, depending on terms and negotiating. I know people that charge higher than 15% and are able to convince people to pay it. It is all about what the market will bear.
OPs: Sometimes the landlord will pay all or part of the commission. These apartments are said to have OPs (owner paid). Numbers here vary as well, but I've seen a half month to a full month, plus other incentives offered on top sometimes. These typically come in slower times of year, or in an instance where the owner wants to get a higher number on the rent roll, because renters love apartments with OPs. These are the apartments that are advertised as "No Fee" typically.
When an OP apartment is cobroked, typically the listing becomes a CYOF. So the listing agent takes the OP and the tenant's agent can set there own price for their commission.
Most of your time will be spent looking for clients. Your brokerage will typically have a pretty good database of open listing and also likely the RLS. You may also have access to exclusives out the gate, or you may have to hustle and find your own if you want them.
The thing to remember with rentals in NYC is that it is a customer service business. People are spending a crazy amount of money and stress and energy on finding and renting a place here. If you can make that job easier and less stressful, then you'll be in business.
Let me know if you have any other questions!
-Matt