KEY POINTS:
The founder of mobile phone group Crazy John's, John Ilhan, collapsed and died in Melbourne on Tuesday while on a morning walk.
The 42-year-old multi-millionaire collapsed near his home in the suburb of Brighton and could not be revived by ambulance officers, his company said.
The company would not confirm reports he had died of a heart attack.
Ilhan, who was born in Turkey but migrated to Australia as a 3-year-old, is survived by his wife Patricia and their four children - daughters Jaida, Hannah and Yasmin, and 8-month-old son Aidan.
Crazy John's managing director Brendan Fleiter said Ilhan was an inspiration to everyone who knew or worked with him.
"He grew a business from nothing to become the biggest independent mobile phone retailer in Australia," Fleiter said.
"John was always a big thinker; the difference was he always achieved what he said he would do."
Fleiter said Ilhan had followed his dream and created a business that employed hundreds of people and provided real competition in the mobile phone business for the first time.
"He cared about looking after his customers and the people who worked with him," Fleiter said in a statement.
"John's legacy will be felt forever in Australia because he offered something new to consumers through his business Crazy John's, which will continue to grow and build upon John's legacy."
Ilhan opened his first mobile phone store in 1991 in the northern Melbourne suburb of Brunswick, according to his company's website.
Crazy John's continued to grow and by 1998 it had 15 stores in Victoria. Today, it is one of the largest independent phone retailers in Australia with more than 120 retail stores and more than 600 staff.
In the 2007 BRW Rich List, Ilhan, a vocal supporter of AFL club Richmond, was the 126th richest man in Australia with a fortune of A$310 million ($370 million).
He grew up in the working class Melbourne suburb of Broadmeadows, where he developed a love of soccer, and went on to play in the National Soccer League.
Telstra said its sympathies were with Ilhan's family and friends.
"He was a long-time partner of Telstra's and it is extremely sad to see somebody die so young, particularly someone like John, who has made a significant contribution to Australia and this industry," a Telstra spokeswoman said.
Ilhan was a strong supporter of charities and in 2006 established the Ilhan Food Allergy Foundation with his wife, after the couple discovered their daughter Jaida suffered a peanut allergy.
The foundation's aim is to support research to determine the causes of food allergies.
He also supported homeless children's charity Kids Under Cover, the Royal Children's Hospital neonatal unit, the Lighthouse Foundation, the Shane Warne Foundation and St Vincent De Paul, among others.
Ilhan had plans to expand the Crazy John's empire into New Zealand, Europe and Asia, according to BRW magazine.
The company this year wound up a two-year, A$70 million court case demanding Telstra repay several million dollars in commissions.
The company had a contract with Telstra which expired in July.
Ilhan told BRW he wanted the business to be worth A$500 million and have 500,000 customers within five years.
His company was seeking partnerships with large telcos for the international expansion, according to BRW.
