S and P lawyer to do the transfer of the property + property TAX

Make sure you value the house as low as possible or even lower than the market value (as you are buying from relatives, i think its possible), this is so that both your mom and aunt, dont have to pay capital gain tax.

Obtain a bank loan to service the remainder of the loan + amount owed to your aunt.

Things to take note
1. get a good rate from the bank
2. make sure you are clear to the bank and lawyers that you are only buying over your aunt portion and the remainder of the house loan.

really depends on which bank you are close with.

I get better rates at the bank where i have premier accounts.