No-fee usually means the landlord is covering the broker's commission, not that no broker is involved. On StreetEasy, if it says no fee and is listed by a brokerage, someone is still getting paid—either the landlord pays the broker or it's an in-house leasing agent who is salaried by the management company. That cost can show up in the rent, but not always. A fee listing might be cheaper over 12 months if the rent is $50–100 lower, but you have to do the math: fee of one month's rent vs a no-fee at higher rent.
If you apply directly through the listing, the agent might still represent the landlord and ask you to sign a dual agency disclosure, or they may try to charge you a broker fee if it wasn't actually no-fee. Don't assume. In outer neighborhoods like Flatbush, some mom-and-pop landlords list on their own with no broker and no fee, but you have to check the 'listed by' field. If it says 'owner' or the management company name, you may be fine.
For rent-stabilized units, the legal rent is regulated but the preferential rent can be lower, and a no-fee may still be tied to a concession. Compare total annual cost: monthly rent × 12 plus any fee, then divide by 12. That's your true monthly. Also check lease length and renewal terms. If you see 'no fee' and '1 month free' on a $2,400 gross, the net might be $2,200 but the lease says gross $2,400. That matters at renewal. Ask what the legal or stabilized rent is and whether the concession is recurring. Good luck.