Hii
I really don't know what exactly free seat means any institute takes a minimum fee Well, most of the IIMs have some scholarship programs where they waive off some fees for economically weak students. If you meet those criteria you would certainly get the scholarship. There are also many merit based scholarships from state and central government and some private organizations.

If lack of money is stopping you to join an IIM. I think you shouldn't be bothered. You can easily get loan at low interest rate and pay them back once you get a job.

Hope this helps