It appears to be legit.

The photo first appeared in The Vidette-Messenger of Valparaiso, Indiana on August 5, 1948. The children looked posed and a bit confused as their pregnant mother hides her face from the photographer.
The caption read: “A big ‘For Sale’ sign in a Chicago yard mutely tells the tragic story of Mr. and Mrs. Ray Chalifoux, who face eviction from their apartment. With no place to turn, the jobless coal truck driver and his wife decide to sell their four children.
Mrs. Lucille Chalifoux turns her head from the camera above while her children stare wonderingly. On the top step are Lana, 6, and Rae, 5. Below are Milton, 4, and Sue Ellen, 2”.
Family members accused the mother of being paid to stage the photo, which may have been part of the story, but unfortunately, she was dead serious about selling her children. Within two years all of the children pictured, as well as the baby she was carrying at the time, were sold off to different homes.