The owner may owe more than back taxes but if the property is worth it, pa the taxes and what ever else.
What you need to do is go to a title or a real estate attorney, but tell the real estate attorney that you want a title policy. You will have to put a dollar value on the house for that.
You at least want a title search. You do not know if there is someone else that may have interest in the property or if there are other outstanding debts owed against the property.