1. Your brother is the owner of 50% of the property which you wish to purchase from him to become the absolute owner of the entire property. The alternative to this is to execute a gift deed whereby your brother may gift the property to you. It would attract stamp duty at a lesser rate.
2. Your brother will have to execute a sale deed in your favour to the extent of 50% of his property. You will become the owner of the entire property only after the sale deed is executed in your favour.
3. The stamp duty will have to be paid on the registration of sale deed. At the time of registration of document in registrar's office you are required to pay the stamp duty as well as registration charges. The registration fee is paid over and above the stamp duty.