I love all the misinformation. As a photographer for over 16 years who just recently got into drones, I can give my MY insight on how the law works, at least where I live (NY) when it comes to photography. Since drones are technically just flying cameras I would think the same rules apply. I do street photography and run into this type of issue all the time.
First, if it can be seen from any public property it can be photographed. This goes for the property, people, objects, structures, etc. I've never heard of any place in the United States where this does not apply. Some authorities who are not up to speed on the law may TRY to tell you otherwise, but they would be wrong....but best to NOT argue with police as they can then get you for other "offenses". You can politely try to educate them (I keep a copy of the photographer's rights in my bag). There is absolutely NO legal expectation of privacy if you can be seen from the sidewalk (or air since that is also "public" and cannot be "private"). Airspace is the sole domain of the FAA. PERIOD. So their rules outrank any local laws in that regard.
This does NOT mean you can photograph INTO someone's dwelling beyond what is visible to the naked eye from a public location. So no "Peeping Tom's" with zoom lenses. People do have a legal expectation of privacy in their own dwellings. (Of course, if they are standing butt naked in the window that sort of negates that expectation of privacy.

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So, anyone telling you you need permission to photograph someone's home from either the street or the air is flat outright wrong. Think about it logically. If that were the case, then taking a picture of a street would be illegal. This would make almost EVERYONE with a phone who has posted a picture of their neighborhood or someone in front of a house a criminal.
Now to get to the OP's actual question. If you did not sign a contract that gave the copyright or exclusive use rights to the realtor you are free to do with your images what you will. IF you did do that, I really hope you got paid really well for it. I would NEVER give up my copyright or usage rights unless I was going to be well compensated. And even then think hard on it. I doubt very you did, but I hope not. You can post away all you want on any platform you want if you own the copyright of the image and there is no contract explicitly forbidding you to use the image. There are those occasions where a client might request the copyright or ask for exclusive rights (usual for a set amount of time) but I doubt this is the case here. So if none of those caveats apply, you can use the images for self-promotion with no worry.