Leave & License Agreement

Hi,

I wanted to give my Grandfather, rent on the property which belongs to him and claim HRA exemption from the company. 

I just wanted to confirm whether is there any need for Leave and license agreement if yes then

Can I print the leave and license agreement on green paper and get it franked instead of stamp paper.

Also what is the amount of franking I need to get.

Also is franking enough or I need to get it registered or have something else done?

Thanks,

Kunal Shah