Warning: this is pretty boring stuff below, but it's what ya need to know. :stoned: If you have any questions pm me. I'm a lawyer who has bought/sold my share of real estate.
You can buy the house from this person at any time prior to actual foreclosure sale, they have legal title even if they owe back payments- but as far as assuming their loan (taking over the payments) that would only work if the lender agrees to you assuming the loan.
Not too likely. The lender probably made what is called a "purchase money mortgage" contract with the owners (they give the money to buy the house). In the US, such "first" mortgages contain a "due on sale" clause- that means if the house is sold, the whole loan amount becomes due and payable. You would need to pay cash or get a new loan from them or another lender to complete the sale.
Lenders don't want to be stuck with a loan on a property where a new owner they haven't evaluated the risks for "takes over," the condition of the property or neighborhood, and prevailing interest rates may have changed since they made the loan.
If you did buy the house, the lender would be paid the back money owed out of escrow before ownership could transfer. Likewise, any other debts the current owners "secured" with their house would be paid, and so would back taxes, and if there is one, homeowners' association dues.
Before you go any further, you should ask your friends how far behind they are in payments & taxes; are there any 'lines of credit' or second mortgages; how much did they purchase the house for; and what it appraised for. Do the math, and you might find out that they owe more than the house is worth.
