Nedd Brockmann will run from Cottesloe Beach to Bondi Beach - a distance just shy of 4000 kilometres - starting September 1.

And if that's not enough, he's set himself the challenge of doing it in 40 days. That's 100km a day. Nedd ... we have to ask: is that even physically possible?

"I'm absolutely positive it is," is the ex-Kinross Wolaroi student's answer.

Mr Brockmann made national headlines in 2020 running 50 marathons in 50 days, raising nearly $100,000 for Red Cross homelessness services.

Days into that effort, as those who doubted he could complete it fell quiet, he began thinking, "what next?"

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Now he's preparing for a coast-to-coast mission - equivalent to nearly 100 marathons - with the goal of raising $1 million for homeless charity.

Mr Brockmann knows he can run, so as he winds back at work to prepare for the journey his focus is on the mental hurdles he'll no doubt face, as well as all the necessary physical preparation.

"I will be getting it done," he told Australian Community Media.

"I'm setting up a routine now - getting my head around what I'm doing. I'm planning how my days look, I'm up at 4 o'clock (in the morning) on the dot.

"Every waking moment I'm devoted to this."

Physically, he's been doing a lot of strength training. In coming weeks he'll tackle some big runs - back to back 50km and 60km runs - but he doesn't want to risk injury.

Between the beaches he'll encounter just about every sort of terrain, from hills to the hundreds of kilometres of straight bitumen across the Nullabor.

"There'll be 12 or 13 nights where we will have to rough it, on the side of the road with the campervan," Nedd said.

"I know they're going to be super-cold mornings, and it's going to be hot in the day."

So what's driving him?

While Mr Brockmann admits he likes to challenge himself, and he's keen for the adventure, this is all about shining a spotlight on homelessness, on the number of people sleeping rough in Australia.

It's a situation that broke this country boy's heart when he moved to Sydney.

He handed out coffees or sausage rolls, even gave away his hoodie, but one person can only do so much, which is how he came up with the concept for his 2020 fundraiser.

This time he's set his sights on a world record for the distance and $1 million for charity.

Proceeds will go to We Are Mobilise, a registered charity that is run by volunteers. They actually reached out to Mr Brockmann, and he's going to head out on an outreach or two with them in coming weeks.

"It's winter now, a lot of people are doing it tough," Nedd said.

We Are Mobilise strives to provide recognition and functional care to the homeless, to educate and raise awareness to the broader society and to be a platform that creates change through connection.

The charity's 500 volunteers have provided more than 500 care packages in outreaches, but they also aim to build trust and connection with those on the streets.

You can find out more about what they do - or even volunteer your time - online at wearemobilise.com

He hopes his big run can "make some noise" on the issue.

"We are more capable than we think we are," he said. "Overwhelming positivity is what I preach," he explains in a video on his website. Get up and go attitude, just keep fighting. There's always something else, one last breath - you've always got enough."

Head online to neddsrecordrun.com to donate.