[citation needed] Kidman was educated at private schools in Norwood and left his home near Adelaide at age 13 with only five shillings and a one-eyed horse named Cyclops that he had bought with his savings.

He made money trading whatever was needed, and supplying services (transport, goods, a butcher shop) to new mining towns springing up in outback New South Wales and South Australia, (including Cobar, Kapunda, Burra and eventually Broken Hill).

[1] Kidman saved money and bought a bullock team, opened a butcher's shop and store at the Cobar copper rush, and made good profits.

[8] Later in 1908, he bought the 700 square kilometres (270 sq mi) Mount Poole Station in outback New South Wales.

Probably his only unsuccessful business venture was the Kidman & Mayoh shipyard, which he established with engineer brothers Arthur and Joseph Mayoh in the Sydney suburb of Putney when the Commonwealth Government called for 24 wooden ships to be built by various companies for the war effort.

The company employed hundreds of men to fell and square heavy timber on the north coast of New South Wales.

With labour in short supply, "bush carpenters" went from the north coast to work in the shipyard, assisting the skilled shipwrights.

Early in 1920 the Australian trading company, Burns Philp, made an offer to the government to buy the two ships.

Kidman lost many thousands of pounds, but was reported to have said that his biggest regret was that the work of the superb axemen of the north coast forests, with their enthusiasm, craftsmanship and loyalty, all went for nothing.

He was well served by his vision of drought-proofing his empire through growing and fattening cattle on the remote stations in the north and bringing them down the lines of stations along the great inland river systems to markets in the south, providing good feed and water on the way to sell them in top condition.

[24] Following a brief illness, Sidney Kidman died at his home at 76 Northgate Street, Millswood (now Unley Park), aged 78, on 2 September 1935.

His body was interred at the Mitcham Cemetery in the presence of hundreds of mourners;[25] his cortege extended for more than 1.5 miles (2.4 km).

Two Chinese companies, Genius Link Asset Management and Shanghai Pengxin, sought to acquire the company, but the sale was eventually blocked by the Treasurer of Australia, Scott Morrison who cited the national interest clause in the Foreign Investment Act.

[35] Kidman’s ‘stonehouse’ childhood home in Athelstone was a heritage listed Building of Adelaide up until 2024 when it was demolished in early May.

[citation needed] In 1936, a biography of Kidman titled The Cattle King, by Ion Idriess, was published; it became a best-seller.