Producing marketing materials for a licensed agent generally doesn't require a real estate license, because the agent is the one representing the seller and the one legally responsible for the advertising. Licensing rules vary by state, though, and the line usually sits at whether you're negotiating, soliciting clients, or holding yourself out as able to sell property. Some states also have specific rules about who may be compensated for activity connected to a transaction, so check your own state commission's guidance before you invoice anyone.
The person who told you a licensed person signs off on anything with a price wasn't entirely wrong about the underlying idea. Real estate advertising rules put responsibility on the licensee and the brokerage. Practically that means the agent must review and approve your material before it goes out, brokerage name and required disclosures have to appear where the state and the brokerage require, and any claim about square footage, price or school district traces back to their data. You're a vendor. Get approval in writing on every piece.
Insurance-wise, the two people usually carry are general liability, which matters because you're walking around occupied buildings with a tripod, and errors and omissions or professional liability for the content work. Some drone photography needs an FAA remote pilot certificate if you're paid for the images, which is a federal requirement and separate from anything real estate.
The thing that bites new photographers is copyright. You own the images you shoot unless your contract says otherwise, and agents often assume a listing photo is theirs forever. Write down whether the license covers one listing, that agent's use generally, or resale of the property later by someone else.
