How should I convince my parents about a career in mathematics? I am an 11th grader and studying undergraduate mathematics and living in India.
I want to become a mathematician, but there is one problem in this path. My parents want me to become a medical doctor, but I have no interest in biology. My parents say there is no career in mathematics and it is a total passion job, you can't get anything from it. They say: "There is no demand of mathematics and you can't go anywhere after few years. The salary is not good and no job as a mathematician. You will only get a job if you do your Ph.D."

So my questions are:


Is it true what my parents are saying?
If it isn't, then what are the careers in mathematics? It is fine if it is a bit long; I don't want any shortcut to success. Also will studying mathematics take up a lot of money?  It is a huge issue in my house.
Your parents are thoroughly incorrect when they say that there is no career opportunities in mathematics. 

Further to Dave Clarke's answer, many (applied) mathematicians find work in the City (as in the financial services sector of London) running risk analyses, for instance. 

If however, you are looking at finding work as a research academic in mathematics, then jobs are there, but sought after. Teaching mathematics at university level provides wider prospects, however. 

To answer your question about money, the amount you have to pay largely rests on the tuition fees that you can afford. This will depend on which university you choose to attend.

There is also the middle ground of studying mathematics with a view to putting that study to work in medicine. Consider that statistics (yes, probably not the subject you are interested in), was essentially developed as a response to a medical situation (plague in London). There is also a vast amount of work requiring pure and applied mathematics in medicine (nuclear medicine, MRI, NMR, for example).