Hi Aspirant!

If you are able to get admission in any NIT by using your OBC category rank, then it doesn't mean you will not be charged any fees. However, there are different rules for each category of students for fees in NITs fixed by the authorities. As an OBC candidate and if your family annual income is between 1 to 5 lakhs then you will be charged around 2, 25,000 for total 8 semesters (4 years). But if the family income is more than 5 lakhs then it would be around 5,60,000 in total. You can check out the complete fee structure of NITs here:

https://josaa.nic.in/seatinfo/root/InstProfile.aspx?instcd=227

Thankyou!