Some get caught up in it and eventually land in jail. In many places, that could mean the end of their lives -- but not so in Hong Kong.
Signs of redemption can be seen all over the city's streets.
Tens of thousands of red, green and blue taxis fill Hong Kong's roadways, and now former prisoners can be found behind the wheel.
"I can't go down that same path," says Ah Ming -- a false name to protect his identity -- as we wind through the packed streets of To Kwa Wan in the city's Kowloon district. "I need to walk the straight and narrow. I need to live a stable, peaceful life."
Ming started trafficking cocaine 10 years ago, when he was just 25 years old. He says he never used drugs but got mixed up in the wrong crowd. He joined a local triad gang and started making frequent trips across the Chinese border to the city of Shenzhen.
"When you want to have a good time you need money," Ming says. "The triads asked me if I was interested in trafficking drugs for them and said I could make a lot of money. I was reckless back then so I agreed to help them."
Ming says he lived the high life for several years, partying and never worrying about cash, until he was arrested and sent to prison in early 2008.
And this is where his story of redemption begins.
While many countries offer rehabilitation and vocational training programs for prisoners, Hong Kong's Professional Taxi Training Course is unique -- and is one of the newer courses offered by the city's Correctional Services Department (CSD).
Ming was among the first to enroll.
Participants learn all about Hong Kong traffic laws, taxi regulations and place names around the city.
"There are around 100 multiple choice questions, so I would memorize them," Ming recalls. "At first I did find it a bit difficult but they did a good job preparing us for the test."
"We're trying to help them reintegrate into society," says Louisa Yeung, outgoing Superintendent of Vocational Training at the CSD. "Having a good job -- a really secure job -- can help them do that."
Yeung says the course structure is designed to help prisoners pass the written exam but it's not the only focus. Character development is also a big factor -- to change mindsets and deter prisoners from returning to criminal activity.
"We want to focus on instilling good attitudes, integrity and preparedness for handling emergencies, so they know how to cope," she adds.
Prisoners wanting to participate in the taxi course have to meet several criteria before being eligible. They must have at least three months remaining on their sentence, but not more than two years. They must also possess a valid driver's license for at least three years -- and cannot have committed any traffic-related offenses, such as accidents or drunk driving, within the past five years.
So far, two rounds of graduates have made it through the CSD's taxi program, ranging in age from about 20 to 50 years old.
For some, the course offers an opportunity to change careers and start anew. For others, it marks their entrance into Hong Kong's labor market.
But one thing most have in common is the reason they were in prison in the first place: Drugs.
Like Ming, some were involved solely in drug trafficking. Others were arrested for drug abuse. And a small contingent was busted for theft.
Yeung says heroin was the drug of choice among prisoners in past years, but it's mostly softer drugs now.
So far, 22 people have passed the course.
But it's difficult to know how many of them are actually working consistently as taxi drivers now. The CSD doesn't track "rehabilitated offenders" after they leave prison. There are no mandated checks or follow-ups.
"If they're a drug addict, the court will most likely sentence them to a drug treatment center where they will undergo a period of supervision for one year," says Yeung. "So within this year, if they relapse we will take action to report them to the center again."
But she says this is extremely rare.
"Most people released from prison are not required by law to undergo supervision. After they're released and go back to society, the department does not have the right to see if they relapse to drugs or not."
Employers serve as a critical bridge between prison life and the outside world. Through the CSD program, "caring employers" from various industries can elect to serve as career mentors by helping graduates land jobs upon their release.
Cheng Hak Wo and his daughter, Sonia, run a business that currently employs three former members of the taxi program. The ex-prisoners make up a small portion of the company's overall 2,000 taxi drivers and 700-vehicle fleet, but the managers say they're also some of the most reliable.
"We're very impressed by them," says Sonia. "They're very willing to learn. We often get calls from them asking how they can improve."
"You just need to be patient," Ming says. "Sometimes you'll get passengers who aren't the best people. They'll yell at you -- and you just have to put up with it."
Putting down a taxi deposit can also be an obstacle for those looking to enter the industry without having been employed for a while.
Ming says it normally costs about 10,000 HKD (US$1,300) for the deposit, but Cheng allowed them to pay 2,000 HKD (US$260) instead, and the rest in installments. In addition, there is a daily taxi rental fee of 400 HKD (US$52), and drivers get to keep what they earn on top of that.
For Ming, that typically means pocketing about 300 HKD (US$39) at the end of a 12-hour overnight shift. At that hourly rate it means he is earning less than minimum wage, which Hong Kong officials just raised in May to a paltry 32.50 HKD an hour (US$4.19). It's hardly enough to earn a living, after you factor in the exorbitant cost of housing and other goods in the city described as Asia's financial hub.
It's also a far cry from the flashy lifestyle Ming was used to leading -- always flush with cash while trafficking drugs for the triads.
But he's undeterred.
"I learned if you want to make money, you should do honest work," Ming says.
He is now focusing on taking care of his parents and hopes to one day buy his own apartment.