Thank you all extremely helpful

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I had asked the question and the reply I had received via email is mentioned above. Since I wasn't sure so thought of asking it on MSG and turned out to be extremely helpful thank you all.
JSNOVER - I have a few images taken on the beach. I saw a wonderful house nearby which was included in the image but I did not enter their premises and the model is the main subject in the images. Do I still need a property release?
I was independent but now am exclusive with IS. I am 99% certain IS would be OK without a property release for a house in the background - not the Disney castle, but a regular house. I do recall some independents mentioning other agencies getting really picky about property releases, but for something in the background with a model as subject I think none of them will require a property release.
@basti. The issue is always risk - how much risk are you and the agency willing to assume. No one wants to end up in court litigating issues - the goal is to avoid that - which means the agencies get cautious and big companies with aggressive laywers (cruise ships, for example) can get agencies nervous.
Not sure how you define "real necessity", but arguably it's nuts for agencies to insist on a model release when the photographer is the model, especially where they insisted on photo id when the account was opened. Also arguably not necessary to include model releases for your own kids (although it might help to have one if a subsequent divorce means things that were once fine are now contentious). I could go on, but this isn't a black/white area. In general, much as I get miffed when something is off limits as RF stock, I don't want to crusade for photographer's rights, I just want to avoid litigation and paying a lawyer over some photo I sold, so I'm OK with agencies being risk averse.