During that time, Khan lived in an empty sewer, went without food for five days, was stabbed, reported to a gang leader of street children and saw his friends lose their lives to alcohol and drug addiction.
Today, his former lifestyle is part of a guided tour that takes curious tourists, mostly Western backpackers, through the chaos of the area around the railway station, home to around 2,500 young runaways and a favourite haunt of budget travellers.
The two-hour tour, launched two months ago and advertised through posters in the area, is the brainchild of Salaam Baalak Trust, an Indian charity for homeless children.
Most children, who run away from home to escape poverty or sexual abuse and sometimes like Khan, to experience the dazzle of big city life, make the station their home.
The busy station provides them ingenious ways -- such as the use of luxury train toilets -- to survive the mean streets. Leftover newspapers are traded for medicine to treat injuries from police beatings.
Discarded fruit is given to juice stall owners to use in exchange for a place to sleep on the shops' tin rooves away from the police's sight.
All these anecdotes are part of the tour which at 200 rupees (4.50 dollars) a head gets an average of five tourists daily and offers a glimpse into the hideaways, hangouts and workplaces of the railway children.
"I wanted to see the streets from a kid's perspective," says 24-year-old US artist Leiv Wold, who in a sarong and beads around his neck and shoulders typifies foreign backpackers looking for a slice of real India.
"Most children watch too much TV. It's interesting to see what children can do when given an opportunity," adds fellow American Aaron Ableman, who is working on a documentary film on deprived children.
With their new jobs, the tour guides have become role models for others whom they meet during the jaunts.
Children with runny noses and filthy clothes greet the guides with toothless smiles at the railway station to try on the tourists' sunglasses and pose for photographs.
The guides also want to change the lives of other urchins and rid the country of problems such as its rigid ancient caste heirarchy.
"People in my village still believe in untouchability and Hindus and Muslims do not socialise with each other. I want all that to change," says Khan, who learnt English in three months as part of job training at the trust.
Apart from being a tour guide, he teaches at the charity and studies for five hours daily to improve his English language skills and complete a degree in social work.
While Khan wants other deprived children to achieve the life he has, 18-year-old Shekhar Saini aims to be a Bollywood actor.
In low-slung jeans and a fitted T-shirt, the acting student at a leading national drama school bears a resemblance to his favourite star Shah Rukh Khan. Even his tourists are impressed with his leadership skills.
"You will make a good actor," says Brazilian tourist Philipe Sá, as Saini asks the group to move with the wave of his hand.
The film aspirant, who ran away from home unable to bear the barbs his parents faced because of his marijuana habit, is now doing his family proud with his confidence.
"My parents are very proud of me today, because I can speak good English and have an ambition. My life in the village was a waste," Saini says.
Around 50 runaways arrive at the railway station daily in hopes of finding a better livelihood, the trust says. Many fall prey to sexual abuse and police harassment, while some take to drugs and others are forced into prostitution.
Most though earn a living by polishing shoes, working at tea stalls, selling flowers and cleaning.
Some belong to organised gangs who earn money by begging and entertaining passengers with singing and dancing.
There are no government figures for the number of street children in India, but according to independent studies, roughly 11 million children live on the road in India.
A large chunk is based in big cities such as Delhi.
"In Delhi alone, there are at least 100,000 children by the most conservative estimate," says Pravin Nair, chairwoman of the Salaam Baalak Trust, which her daughter and internationally-celebrated filmmaker Mira founded in 1988.
The charity was initially launched to help deprived children who acted in Mira Nair's acclaimed film "Salaam Bombay" -- a gritty tale about life on the streets -- which won a national award for its lead actor.
Since then, the organisation has helped in rehabilitating around 3,500 children and ultimately uniting them with their families.
"These children want to convey what they can become if given a little help. The street tour project is a celebration of their lives," Pravin Nair says.