In his youth, Jens spent some years abroad and studied in Paris with his brother Steen Clausen Bille (1527–86).
Their tutor during the journey was Christiern Mortensen Morsing, later Professor of Dialectic at the University of Copenhagen.
After Jens's return we find him in 1555 as the Hofsinde at the court of Christian III of Denmark, and here he spent the following year.
As Hofsinde he served at Hoffanen in the Last Feud between the King of Denmark and the Ditmarsians immediately after Frederick II of Denmark's accession to the throne and took part in the battles at Meldorf and Heide.
It was the youngest son, Steen Jensen Bille (1565–1629), who later took over the farm on his father's death.