When you speak of being any professional sport player, it simply means you are paid to play. The amount can be as small as Re 1 to the limit you cannot even think of.
I don’t know your background, so I have to answer based on scenarios
Scenario 1: No experience, just started playing tennis for recreational purpose
- What tennis data is most important to players and coaches?
- What is the tie-breaking rule in tennis?
- Quelle est votre stratégie de tennis préférée?
- Who has the best chance to win Wimbeldon 2017?
- Is Roger Federer's Sneak Attack By Roger (SABR) a disrespectful shot towards the opponents?
Sorry to say, its too late to apologize. By the time you complete your engineering degree, you’ll be around 21–22 years. And to become a professional tennis player you have to start as early as possible.
Scenario 2: Playing for a long time, represented at state level or won several college championship.
It means your basic are good, and you are well above the average lot of people. Now you need to find a very good coach, who can guide you and focus all your energy and aggression towards a common goal which means gaining expertise at a pro level, better techniques, best footwork.
At this age, you have to train at professional level else, your body will find it extremely difficult to cope with the physical demands. Mentally, you’ll still be a kid on the court. Match experience is something you gain only through, well, matches. So to reach the mental level that other professionals of your age have reached, you’ll have to play a lot of matches every week which will be very tiring.
PS:If your planning on taking the risk of being a professional tennis player, my personal advice would be to not do it. It’s like putting your life on the line for a lottery. The odds of you winning are there, and that too very less. But then, miracle do happen.