I'm sure you covered this topic somewhere but I could not find it. I was checking in with a friend of mine and I wanted to send him some shots I did of a home. The files were too big so I just gave him the MLS number. Wondering what would happen if he just googled the MLS number, I did it and to my surprise, my photos were in about 12 different real estate firms. Let's see now, I was paid by only one firm. Is this normal?
Yes, if you shoot images for a listing agent and they upload those images to their local MLS then those images will automatically be spread around (syndicated) to all the local broker sites, regional sites and national sites.
This process is referred to as real estate listing syndication. For more details on how this works see this site.
As long as the listing you shot is active your listing photos will be on far more than 12 sites. It's more like thousands of real estate sites. Here is a list of the national, regional and affiliate sites that listings get syndicated to. This doesn't even include all the brokerage office sites or Realtor sites. Individual Realtors can get a feed of all the listings for their local area (called an IDX feed) for their personal sites. This is the way online real estate marketing works. The theory is the more sites that have the listing on the more potential home buyers eyes you get on the listing.
When listing agents upload their listing photos to the MLS they get to make a choice if they want their listing syndicated. Back in 2012, there was an agent movement against syndication but I think it disappeared. In the end analysis, it's in the home seller's best interest to advertise the listing as much as possible. Sure there are abuses in this current real estate listing syndication process. But most listing agents think it gets the job done.
So in summary, your photo licensing agreement with your listing agent clients needs to allow syndication because it all happens automatically if listing agents allow syndication of their listings and most listing agents do choose to syndicate their listings.