Great to have the new forum, thanks!
My son has taken a stunning photograph of and from the platform of our local British Rail station. I think there is potential (small) market for a postcard or a greetings card using the image. There are no identifiable people in the shot.
Would I need to ask permission from anyone before creating and selling the photograph?
Taking the picture is not against the law. Selling it might be without a property release from the owner of the property. I will leave these links here in the meantime for you and others to read.
Further reading should you want some: Photographers Rights: the ultimate guide from Techradar and The London Skyline - an IP view from Fieldfisher.
Hide in the noise. #hackerwisdom
I see no difficulty in selling it. A buyer might insist on a release, but the insistence would be without merit.
I do caution however that from distant memory, there may be anti-terrorist legislation which restricts photographing public buildings of certain sorts. It included Police stations, but that was not the only limitation. Such legislation tends to be self expiring, so I do not know, but it may be worth checking.