Why would you want to assume payments on a home that is pre-foreclosure? Generally pre-foreclosure properties are worth less than the balance owed (mortgage, late fees, attorney fees, etc), which is why the current owners are not selling outright and paying off what is owed.
Plus, assuming payments does not equate to conveying title/ownership of the property. You could end up making a number of payments on behalf of the current owner and the property could still end up being foreclosed upon by the bank.
Before you do anything, please take any agreements you are about to sign to an attorney for review and get the full picture as to what can happen afterwards should you assume payments.