A Heidkate originally was a one single house where people and live stock lived under the same roof (this was usual in Germany) and in the course of time a handful of smaller barns and other little cottages would have been added.
Typical cottage. A man owning such a home was called a cottage man. He was near but not at the bottom of the "social ladder". Below him were lodgers, workers, "instmen" and clients of the poor box. These cottage men frequently rented out part of their homes to lodgers and their families the result of what often were up to 20 people living in such a cottage...
The image "fisherman's cottage" shows that this cottage is directly at the beach. The subscript telling that it belonged to Wentorf was part of "Wentorfer Strand" ("Wentorf Beach").