Hello @James A.,
The bank holding the mortgage will require that a realtor present the short sale offer to them. Short sales 1-3 years ago could be very profitable because the banks were more willing to take deeper discounts. Today it is more of a challenge to get enough of a discount to make a flip work. That said though, deep discounts are difficult to find in most markets from most sources, and I would pursue it because you have a willing client at the table.
If you do not have a very good short sale realtor I would try to contract with the homeowner then find a short sale realtor. You want to find a very experienced short sale realtor that is on board with your concept of buying and reselling. Remember, you are bringing the deal to them. Many are so focused on the current as-is market value. You want one on your side that is focused on how to justify a fairly deep discount understanding that this is a distressed asset - not your cleaned up, repaired, ready of immediate occupancy type of property typically listed on the MLS. You want a very experienced one because the process, and especially the price negotiation, can be time consuming and at times frustrating, with the bank taking months to approve the short sale. However, your seller will be able to stay in the property while the short sale is underway, unless or until the bank decides to foreclose.