Mhada property transfer

Hi, I had recently applied for a MHADA flat in Mumbai in the name of my retired mother. I had applied in the name of my mother because I was not eligible for this govt housing scheme from an income group perspective. The scheme was for Lower income group(LIG) people. My mother fits into this category. We won a house in the lottery. If we decide to take up/purchase the house then it can only be done in the name of my mother. There is a lock-in period of 5 years. After that the house can be transferred in my name. But my mother doesn't have any money for purchasing this property. I will be helping her with all the money required for this house purchase. So, technically the house will be in the name of my mother but totally purchased from my money. My mother will be transferring the house in my name after the lock-in period is over. I also have a younger brother. He has no objection with the above arrangement as he is not paying for this house. However, we never know how one would behave after 5 years. Thus, I want to understand what can be done legally in advance to facilitate this transfer of property in my name without any complications after 5 years? Can "Registered will" help? Or/and "Power of attorney" will be required? Kindly advise the best legal solution for the above mentioned issue.