By Andrew Walker
BBC News, Johannesburg
In a quiet street behind Johannesburg's Park bus station, Warren waits for customers for his minibus to Zimbabwe.
Zimbabweans entrust lifesaving supplies to drivers live Warren
Buses arrive every day dropping migrant workers in the city, but not many have time to go back home because they are so busy working.
But Warren doesn't take people, he takes cargo and money to migrant workers' families.
They trust him to take sacks of maize meal, rice, oil and hard currency back home where people desperately need them.
Warren is one of around 20 bus drivers, standing around chatting and chomping on watermelon, waiting to fill their buses.
"We take things for about 20 or 30 people at a time, depending on what they want to send," he says.
A small box can cost 200 rand ($20, £13) to send to Harare, bigger sacks cost much more.
They also take envelopes of hard currency to people waiting in Zimbabwe, for a price.
They charge a 20% commission on 1,000 rand.
But Zimbabweans don't have much choice as electronic money transfers don't reach rural areas.
And their own currency is now totally worthless, teachers can't even buy a loaf of bread with their monthly pay.
A ragged cardboard sign shows his destinations, but he'll take a delivery right to the customer's door and then phone them when he's back to say "job done".
David, a 26-year-old painter has been using these minibuses for two years to take back food for his family.
He has seven people to provide for.
"Only three are working, but that isn't enough, there's nothing to buy, nothing."
The whole system works on trust.
"It wasn't easy the first time to trust them," he says.
"I kept calling them constantly finding out how far they had got, but when my family called to say they had received it, my mind was settled."
An estimated three million Zimbabweans have gone to earn their living in South Africa, as their economy has collapsed at home.
The bus drivers are anticipating a rush in demand at the beginning of December, as people start sending things back for the festive season.
With no end in sight to the crisis, these couriers will be in business for some time.