Enlist two dozen recruits from the community and send them deep into the bush for 30 hours under the guidance of ex-special forces troops to raise money for the Terry Campese Foundation.

"If everyone can raise $1000 each, that'd get us a bit over 20 grand and we thought how good would that be," Campese said.

The simple idea has grown into a monster.

As of Thursday, the recruits had raised more than $130,000 ahead of what's been dubbed "Hell Weekend" on February 26-27.

They've been training regularly at Scott Williams' Crossfit gym in Hume, and last weekend were put through a grueling hour-long session at Lee Campbell's B.Firm obstacle course in Narrabundah, replete with neck-deep mud, skin-ripping sandpits and torrents of verbal abuse.

The recruits have only been given an itemised list of gear they must bring to hell weekend - 'no more and no less or there'll be consequences' - and a starting time and place.

From there they'll cede complete control to a crew of ex-military personnel who will take charge for 30 hours. The more money the recruits raise, the more punishment they'll endure.

"The unknown is the scariest thing, the fact that we only have a starting point and 30 hours ahead of us is terrifying," recruit number six Nicole Bell said.

"Who are we going to see, what are we going to do, what are we going to eat, where are we going to sleep?

"I've never done anything like this, I'd never even seen the SAS show on TV, everything that I've researched in the training is not what I was expecting at all.

"Physically I'm pretty strong, I have good endurance but I think mentally that's what's going to break me. Pushing myself mentally will be the hardest I think, on no sleep and no food. Usually I'm a happy person but when I don't eat food..."

After 10 years raising money for disadvantaged youths and homeless people, this month's Special Forces Challenge has quickly become the charity's largest endeavour.

Funds raised will go towards this year's youth program - an annual initiative aimed at disadvantaged youths which includes a 20-week mentoring program, culminating in a week-long trek. Last year they did Larapiinta in the Northern Territory, while the program has also undertaken the Kokoda Track.

"Some of the kids have been through what you wouldn't wish on your worst enemy," Campese said.

"From highly traumatised backgrounds, foster care, thrown around from pillar to post, parents aren't around due to a range of different things, drugs and alcohol being the main ones. Some of them are very, very sad stories.

"When you do Larapinta or Kokoda, there's no phone reception, it's all about communicating and being out in the wild, it just brings everything to the table. That's where great discussions are had. That's what this program does, it builds confidence."

Recruit number 26, Shane Tipa, has spent years helping rehabilitate men who have hit rock bottom through his passion for training and discipline.

"It's more important to work with the youth early to minimise what you have to do with them later on in life, to get them to understand, and these are the sorts of programs that create that opportunity and initiative," Tipa said.

"I've done a lot with broken men and helping them get over things, making them mentally stronger and changing their lives.

"It's guidance, it's leadership and it's getting them to understand it's who they mix with at the end of the day. Show me who your friends are, I'll show you who you are."

Campese said the Special Forces Challenge would become an annual event.

"This is here forever, I've been inundated with requests to be a part of it," Campese said.

"We're full for this year but we could fill probably the next two years with the amount of people that are interested and want to be involved."