Dear Pritam, considering the fact that you are asking this question before studying 12th as you haven't selected the course yet, you must be 15-16 years old. Now by the next 10 years you want to buy a BMW, a nice house, a good lifestyle and you also want a job that allows you to travel. Let us break the career path for you. You study 10+2 for 2 years and by then you turn 17. (8 years left). Then you appear for a relevant entrance examination either JEE or NEET and then if you have really worked hard, you get a seat and join the Professional Course. 4 years for B.Tech and 5.6 years for MBBS( which means you are left with 4 years if you take up B.Tech and 2.6 years if you have selected MBBS). Now if you are lucky and get a job immediately as a fresher, you get an annual package of 4lpa max in Engineering and 5lpa in MBBS. Now your salary hike doesn't happen every year and even if it does happen, there is a Bell curve that is followed and n o body pays you 1000% more than your last pay check. So in reeality, to go from 4- 5 lpa to salary enough to get  you a BMW, in approximately 3-4 years is impossible. But if you get an onsite opportunity in Engineering field, you may earn better than a doctor.