The first step would be to pull up all the active, pending, sold, and expired listings. Next you need to see how much the sellers owe the bank on the home and how many banks are owed. This will help you to come up with a good price. The bank isn't going to take too big of a loss. I am seeing about 80% of what is owed.
Let me just say that every short sale is different and every bank and agent handles them differently. Make sure you get an agent with shortsale experience. This can be a very long and drawn out process, but with the right agent behind you it can make a difference.
It really depends on the BPO (Brokers price opinion-market analysis). Some lenders will pay 3% of the purchase price towards the buyers closing costs. Some will pay all of the buyer's closing costs if they are netting 88% of the BPO amount. You also want to make sure if there is multiple offers and offer accordingly.
With short sales you should have your Realtor do a little research for you. The first and main thing is to find out if the listing agent plans to submit all offers or just the first offer and take back ups and how the Realtor came up with the price (did they start too low to bid the price up or is it close to market value). Then your Realtor should run comps for you to determine what is market value. If the you will be competing against multiple offers submitted to the bank I and you really want the house. I would offer at least $5,000 above asking price if it it is priced low. If it is priced right you should offer asking price. To answer your questions, if there are multiple offers I would not ask for closing costs. If you will be the first and only offer I would make the price strong and ask for all closing costs, pre paids, and prorations. I have represented many buyers where the bank has [aid the buyer's closing costs, it is not a deal breaker. As long as the numbers work for the bank, meaning they will net the amount necessary, then they should approve it. If not, they will counter. Financing plays a part in the offers too. Cash is best ( if the price is right), then Conventional, last VA and FHA. A bank would rather sell to a person wanting to live in the home rather than to a low ball cash investor, but if you're the only offer, better for you.