Wondering how to purchase home from family member?

My significant others grandmother is looking to sell her house before she is to old to me and my significant other. She wants to do this at a below market value price. The reason being largely that she doesn't want her estranged daughters chewing up any of the estate, and wants the houses to stay in the family.

Trust me us getting the houses is the only option. With this being said, we would like to give her some money (somewhere in the $300,000 range) using a mortgage.

Is the best way for this to happen by using real estate agents? Or could she somehow gift the houses to us and we give her the mortgage money.

Thanks
Added (1). This is in Canada

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