Lang Walker knows a bit about property development and investment – he's been doing it for the better part of 40 years and became a billionaire twice over in the process.

During his time, many a developer has soared and then crashed. If one thing has distinguished Walker, it's been his ability to sell out at the right time, or close to it, and come back to the party later. He's been as much a trader as an investor.

While the Walker empire is always open to deal, he has two major sell-downs on his corporate CV: In 1999 he sold his stake in the then-listed Walker Corporation to Australand – the dot-com bomb hitting the next year didn't damage him; and in 2006 he flogged a $1.25 billion portfolio to Mirvac – and his business kept growing through the GFC.

And now he's attempting his biggest sale ever – about $2.5 billion for Melbourne's Collins Square properties. There might be a lesson here somewhere.