Great questions Confused Buyer. In nearly all cases, as part of the short sale negotiation the bank will pay any commissions. However, if you engaged a REALTOR as a Buyer's Agent to approach a private home seller that may be in distress but not listed on the Multiple Listing Service, and you have agreed to a buyer's agency agreement agreeing to compensation (commission) then you may. Even in that scenario the bank would most likely be willing to pay the commission.
We have found that banks are higher to the purchase price offered as opposed to the net they receive. Some agents will attempt to manage the transaction and paper chase of financial docs from the seller which can be problematic. We prefer to engage a short sale negotiator, like Bill & Denise McCormick of CK Capital Management, in the process to keep the process moving along fast enough to be practical. Did you find a good short sale property to make an offer on?