It may not give you an advantage, if the seller owes more than what they are asking for, or close to the asking price and they may have to pay the bank late fees and fines. This might become a short sale and then even if the seller agrees to the price you offered, the bank will need to approve the short sale, unless the seller comes up with the difference at closing, which most likely they won't because they probably don't have the money to do so.
Another option that might give you more bargaining power is looking for a bank owned home or REO. They want to sell, it usually will be a very quick closing but you will buy strictly as is and they will sell for the market value or lower, they are not looking to make a profit. You have to do your homework upfront and make sure this home is what you want, home inspections, etc. Sometimes you can get a great deal. Find a "buyer's agent" to represent you because the agent for the bank will not be able to, they will have the bank's best interest in mind, not yours.