Pani puri is actually an Indian snack and may have been used as a snack by other people who shares border with India. Nepal borders with India to South, East and West and that's how this snack has been available in all parts of Nepal. Except in mountain region, to the north part of Nepal, I think this is not available. Just like dumplings, you can made a pretty handsome salary by opening a pani puri shop. These shops are more frequent in every streets of Nepal.
In the past, people from southern part of Nepal, who is both Indian and Nepal, used to do business in whole of Nepal. As the taste of pani puri gets popularity among children, teenage and aunties in the age of 35-50 years, gets popular, this business has been adopted by many Nepalese from every caste, sex, ethnic group as a means of earning money. And no doubt, you would be pretty successful in earning. Just don't serve unhealthy to the customers, you won't earn their trust.
My mom is a lover of pani puri and I prepared this for her, I don't love it but I eat from time to time when I am out in the street with my friends. Here are some pictures from pani puri making.
Cooking puri in oil.
Puri ready from frying up with oil.
This is a spicy and sour flavoured drink (pani) to accompany with puri and the puri is incomplete without it. No taste.
A mashed potato mixed with different ingredients like onion, green pepper, coriander, peas.
This is how pani puri is eaten, you make a hole in that ball shaped puri made from wheat and then put the the mashed potato mixed with different ingredients and then spicy and sour flavoured water.