IF this is a foreclosure, there is no mortgage amount, because the bank owns the property and the bank doesn't have a loan on the property. The prior owner's mortgage means nothing, it is gone (along with their credit). IF this is a foreclosure, the present owners are the bank. IF this is a foreclosure, the property taxes are not outstanding, because the seller (the bank) has (likely) paid the taxes up to date and will convey the property with clear title. IF this is a foreclosure, the buyer will pay his/her closing costs. The ASKING price is determined by one or more broker price opinions performed by local realtor assigned by the bank, and usually accompanied by an appraisal. The SELLING price is determined by the highest price a ready, willing and able buyer will pay for a property. It's also the lowest price the seller of that property will accept. Lastly, the lender can sue the former owner for the deficiency of the mortgage if they wish, which would have nothing to do with you as a purchaser of the foreclosure.
If your questions were in reference to a short sale, then my answer means nothing to you. You mentioned foreclosure several times, and never mentioned short sale.