Tax Sale

I live in a house that is paid for but my father in law as yet to take the house out of his dead mother's name and put it into either his or our names and we want the house in our name asap so i can fix my house and use the extra to invest in some other properties.
There is still money owed on taxes because he doesn't pay it all the time and they aren't really that much but my family could use the money really bad. How can I get this house in our names without spending alot of money and we will own it and maybe be able to give his dad some money to fix his own house.