Create instant equity with short sale

Recently, I purchased a property where the owner is in short sale condition. This is one of the golden market to invest real estate and could potentially create an instant equity for investor.
What is short sale?
Short sale happen when the borrower fail to make mortgage payment and before the bank take legals steps to foreclose the property, borrower ask the bank's permission to sell at a price lower than the outstanding mortgage balance.
Why would the bank accept?
Two reasons:
1) Bank may suffer more loss due to the lawyer's fee associated with foreclosure process
2) Bank is not in business owning home. Any non-performing mortgage bank carry will negatively affect its balance sheet and the financial strength to approve more loans in future. Therefore, the bank would rather get rid of these non-performing mortgage to reduce its loss.
How do you find this deals?
Newspaper, MLS, agents. I bought mine thru agent who specialize doing this kind of short sale deal.
How much below the market price (or mortgage balance) can we buy?
Depends if the bank is flexible enough. The house I got was at at least 10% below the market value or 30K. This means I instantly create an equity on paper when I acquire this property.