Well there are two best ways to get into merchant navy in India,

1- one year Diploma in nautical science
2- three year BSc degree in nautical science.

then you have to clear IMU (Indian maritime university) CET exams. 
if you will search on on IMU website you will get the information regarding the admission process and dates of entrance.

DNS is the best option because you will earn early and after 1 yr shore training you will be joining ship and after minimum 18 yrs of the sea service as a Deck Cadet you will be promoted to 3rd/2nd officer after you clear your 2nd mates exam.

So first take sponsorship or join in good colleges such as Anglo eastern maritime academy , Great eastern maritime academy , Samundra institute of maritime institute , Tolani maritime Institute.etc

because first they provide sponsorship then your admission is confirmed and after course completion you will placed in your sponsored company.

Hi Ishaan.

Great that you wish to be a cadet officer in merchant navy.Merchant Navy, as the name suggests is the term is the term for commercial marine services.The commercial naval activities in India include shipping of cargo and people across various destination of the world.If you love to travel then it is a great job for you as you'll be travelling around the world for the completion of your task.

To join merchant navy you have to appear Indian Maritime University examination which is known as IMU CET.The IMU CET is conducted around 1st week of June.There are many other colleges for which can be considered which include :

1)Tolani Maritime University

2)International Maritime Institute

3)B.P.Maritime University.

4)TMS Chanakya

5)NMA Chennai

The last two colleges accept JEE scores as well.All the colleges accept IMU CET scores.Tolani conducts its own examination.You can appear for AIMNET as well.

Attaching some links for your detailed knowledge

1)http://aimnet.net.in/

2)https://university.careers360.com/articles/merchant-navy

Merchant Navy, as the name suggests is the term is the term for commercial marine services.The commercial naval activities in India include shipping of cargo and people across various destination of the world.If you love to travel then it is a great job for you as you'll be traveling around the world for the completion of your task.

To join merchant navy you have to appear Indian Maritime University examination which is known as IMU CET.The IMU CET is conducted around 1st week of June.There are many other colleges for which can be considered which include :

1)Tolani Maritime University

2)International Maritime Institute

3)B.P.Maritime University.

4)TMS Chanakya

5)NMA Chennai

The last two colleges accept JEE scores as well.All the colleges accept IMU CET scores.Tolani conducts its own examination.You can appear for AIMNET as well.

Attaching some links for your detailed knowledge

1)http://aimnet.net.in/

2)https://university.careers360.com/articles/merchant-navy

Dear Ira,

Firstly for merchant navy you need to give CET this may 2018.
Then, coming to your query, fees vary from institute to institute. As Government institutes will be cheaper than private ones.
Government institutions will charge near about 2-2.5 lakhs per annum. Whereas in private institutions it will be 4-4.5 annum per lakhs.
The fee structure include hostel, tuition, food and some stationary.
I hope this helps.
If you like the answer, kindly up vote!
Good luck.