What To Do With 300K House in Brooklyn

[Mary Ann]

I know someone whose father is deceased and he wants to buy his sister out of the house. 

The sister name is on the deed, etc.  The sister wants to be bought out of her 50% and free of the property.  There is 300K mortgage left on the property valued at 670K.    It is a single family 3 bed 1 bath with basement. 

 He is new to investing and wants to leverage the property to eventually buy a home down South.  He wants to use the house as an income stream, and start investing.  He's worried his poor credit may prevent him from mortgaging the house.  

What is the best strategy to leverage the house to invest in other properties, rent the property (airbnb?) vs him just taking on the property and doing nothing? What would you do if you were him?