well.. its an arduous question to answer. If you have good command in hindi, passion for music, good voice and confidence... then yes! you sure can become a playback singer in bollywood. As far as I know, Mumbai is the place where bollywood industry exists and runs. So first get training from a music teacher in order to become expert in singing. If you are in university/collage, take music as your subject, it will further help you to reach to your goal of becoming a singer. If you are self-reliant, assiduous and if you are able to devote your 100% in your particular task, then you'll sulery earn. Good luck for your future endeavours!