Yes it is, many people in the world play professionally or teach tennis.
yes
Tennis is a sport just like soccer and football Just to have fun or it can be a career
Eric Fromm is a retired tennis player from the Unites States. Fromm's best result in his tennis career was reaching the fourth round in the French Open in 1993. He was beaten by Jimmy Connors.
Sharapova
Pro Direct Tennis sell a variety of products that will aid anyone who want to pursue a career as a Tennis player - including tennis clothing, tennis shoes, tennis balls, tennis rackets and even a free personalisation of tennis rackets.
Toni Nadal
They are professional Tennis players.
yes
Lindsay Davenport supposedly has the highest career earnings ... in the 40 Million area.
yes.
9-10 years
Probably not much math education. But you should probably make sure you're good at tennis.