@Account Closed typically someone isn't going to give you a discount just because they have equity in their home. That wouldn't make sense on their part. (Assets - Liabilities = Equity) Therefore, the value of their home must be greater than any debts they owe on the home. You can get the value of the home by running comps yourself or asking a real estate agent in your area to do so. As far as debts, the only way to get information on that is to get a title search. That will show all outstanding liens against the property.
@Account Closed they have to bring 50k to the closing table to pay off the rest of the loan.
@Account Closed Then they can't sell it. Unless they can get a short sale approved with the bank. But that's a lengthy process and requires a lot of documentation and proof that they can't continue to pay the bills.
Value of Home - Outstanding liens = equity
Figure out the value of the house. Figure out the amount of debt that have against it. Subtract.