The short sale process timeframe can vary from property to property, lender to lender and thus from either the buyer or seller perspective.
if you list it for a short sale typically the bank or lender wants to see an offer. Some short sales are started before an offer is submitted and approved thus cutting time for a purchaser. If you are buyer submitting a short sale I would anticipate roughly 120 days or longer for closing. Sometimes they happen faster.
An offer is submitted and the seller agrees to the offer. it is then submitted to the bank for approval. They normally conduct a BPO for estimated value of the property. it is submitted to the bank/investor for approval.