Should I buy my mother's home in southern CA?

[Vanessa Estavillo]

The situation:

-I have one rental property right now and am looking for a second 

-My parents are divorcing and want to sell their 3bd 2ba home but still owe $470k on it. According to zillow, it's worth around $535k, someone has offered them $550k

-I would like my mom to be able to still live in the home, so I was considering trying to pay my step-dad off so he can move out

Should I:

-Try to buy the house from them for what they owe the bank ($470k) and give my step-dad his share in cash?
(She can live there, and we can rent out the other two rooms)

-Is there a way to put the property under my name/share the title with my mom instead of "buying" it?

-Try to turn it into a duplex, each unit would be a 2bd 2ba?

Any and all suggestions/advice are appreciated!