Short Sale Promissory Note?

I am the buyer in a short sale. Seller's loan is with Bank of America. We just got Short Sale Approval today; however, B of A is requesting that the seller sign a promissory note to repay bank $15,000 over an 8-year period. Doesn't sound too unreasonable but the seller has opted to "negotiate" the terms of the promissory note. Obviously you can't put yourself in the seller's shoes, but do these "negotiations" take long once Short Sale Approval was granted or do these situations usually drag out for a few more weeks or months? This wait so far has been BRUTAL.