My father (deceased) left a house with a join name of my mother & my brother and me

This is an old house which loan already settle 10 years ago. My brother and my mum need some cash urgently.

- My brother agreed to sell his 1/3  to me amount to 150k &
- My mother agreed to sell her 1/3  to me amount to 150k

Questions:
1) I don't wish to borrow loan but to pay off 300k cash to them. How should I proceed?
2) Do i need to engage with any lawyer to state clearly the pay off of this 300k amount ?
3) What are the fees need to take into consideration with this scenario?

Thanks !