Great question and so there is the legal answer and the practical answer.

The legal answer is that unless it is your own property, you must be a licensed agent to receive compensation for acting as a leasing agent if you are doing it as your own business. i.e., if you are calling landlords and telling them you can fill their apartment vacancies and you would receive a fee each time you find a qualified candidate who ends up renting, then you do have to be licensed from the legal perspective. If you are on the payroll of a leasing company however, then you are paid as an hourly employee with commission based compensation.

The practical part of this as you know is that real estate agents & associations only care about Listings, Buyers, and Sellers of Property because that is where the largest commissions are. You will likely be able to be paid under the table for every vacancy you fill in an apartment and no one would ever know. You will want to avoid dealing with any realtors or agents (unless you know them to be cool) and essentially build your business by finding "Supply", i.e., landlords who have a lot of apartments to rent.

Once you have the supply, you then simply list them on Craiglist and your phone will ring off the hook.

Prior to my current business, I ran my own property management and leasing company and rented 85 apartments in a year, so I know this business well and rentals are simply not high up on the list of areas where local associations or government agencies try to crack down on, unless of course people are getting ripped off by people flat out lying about their connection with properties and getting their security deposits stolen.

In other words, if you act with integrity, you can make a good business renting apartments. If you want to schedule a call with me as well, I can give you my business model in a consultation if you want pointed advice.