My husband and I have started a tilapia farm here in Brazil. Because you are in India, the temperature of the water should be perfect. Therefore no cost to heat the water. The start up cost will determine how quickly you want the business to grow. There are people using children's swimming pools to raise tilapia.
Here in Northern Brazil, the market needs to grow by 40% to supply the amount of fish they require. I didn't believe this until we started to sell. My phone was ringing from 6am to 7pm.
We had no experience in this before starting and have made some mistakes, but there is a vast amount of information available on the internet. It can not only provide you with an income but also with a enviable outdoors lifestyle. I have never been in such great shape. It is manual work but very gratifying.
Just to put it in to perspective for you. I am 51 and my husband is 61 and an amputee. We were computer engineers in Europe and wanted a complete lifestyle change. This is what we have decided to do here in Brazil and are loving every minute of it.
Whatever you decide to do, good luck to you.