So, the following numbers show the magnanimous size of the begging industry in India.
According to a study made by a sociologist from Hyderabad Mr. Mohammed Rafiuddin, 73,00,000 beggars across India who earn as much as Rs 180 crore (Rs 1.8 billion).
And that is a survey conducted across all the top tier towns in India. And the cities like Delhi and Mumbai, which are the National capital and the Finance capital respectively, sits higher than the mean.
The study put the number of beggars in Hyderabad at 11000 with a total earning of Rs 1.5 crore.
And as Dave has mentioned in his answer, this survey would give a better insight into the earnings of the beggars in Delhi.