Selling photos on Flickr? Or can people download them just like that?

Hey guys, I have an Alamy and 500px profile where I upload my good photos and license them for potential sales. For my job a publisher asked me to show my portfolio and suggested I upload it in albums on Flickr. However, it's the same photos that I am selling and I didn't find an option to sell my photos after uploading them on Flickr, I looked up an option to disallow people from freely downloading the photos (viewing is good!) but it seems that viewing and downloading is considering as one and I can't block one to allow the other.

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Am I missing something or should I just tell them to view it on my other sites.