i am planning to buy a short sale. should i hire a lawyer to help me in addition to the real estate agen that i am going to use.

You're asking a lawyer if you should hire a lawyer - so of course the answer is going to be YES !  But seriously, with a a short sale, there is another person at the closing - the bank.  The property is being sold by the current owners, and you are purchasing, but the bank also has a "say" in what goes on.  There are so many short sales occurring that the banks are often overwhelmed and things get lost, or issues do not get resolved.  The property is probably being sold "as is" and you may not have a chance to do a proper inspection.  It is best to hire a lawyer that can protect all of your interests in this type of sale.