This weekend, the six-strong Dunedin Street Football team, including Mr Aitken, competes in a four-team national competition, with each player hoping they will be among the eight selected to represent their country in Rio de Janeiro, Brazil, next September.
It had already been a life-changing process, team manager and Pact community support worker Jason Whyte said.
"Among the team we have players who have epilepsy, are bipolar and have intellectual and physical abilities," he said.
"Despite that, they play hard and are dripping with sweat at the end of each training session.
"We've seen huge benefits to health and wellbeing, for instance giving up smoking, losing weight and setting goals.
"Seeing them develop as players and as people is very rewarding."
Take for example Mr Aitken.
After several years of alcoholism, the Dunedin team's striker has not had a drink in three months.
"I like to win," Mr Aitken, who had not previously played much football, said.
"And we're learning to play as a team."
Dunedin will play Auckland, Wellington and Christchurch in the Street Football Aotearoa competition in Wellington on Saturday.
Mr Whyte believes two or three of his players might make it into the New Zealand team, which will be among 60 national teams attending the 2010 Homeless World Cup.
"It's an opportunity of a lifetime," he said.
"Given their financial situation, for most of these guys it might be their only chance to travel overseas."
In New Zealand and other developed countries, the competition's homelessness criteria has been broadened.
"Because there is not the same level of homelessness, players have to be people with an intellectual disability who, but for government benefits, could be homeless," Mr Whyte said.
The Dunedin team's members are drawn from Pact social football teams and have been training together for four months.
Pact supports people with intellectual disabilities and people recovering from mental illness.
