[1] In 1549 (4th year of King Myeongjong), Gu Sa-maeng was appointed as Jinsa (진사).
In 1558, at 27 years old he passed the national examination as a military officer and worked in Seungmunwon (승문원; 承文院) as an inspector.
From then on, he started to serve in numerous government posts in the central and local areas during the reign of Seonjo of Joseon.
Meanwhile, during the Imjin War (임진왜란), in 1597 (30th year of King Seonjo's reign), Gu served some of the Royal Princes.
So he didn't own land or a house, but only enjoyed his coat of arms ("천성이 담백하고 조용하였으며, 검소한 것을 좋아하여 땅이나 집을 장만하지 않고 오로지 문장을 즐겼다.").