standing water
this house i am looking into flipping has a low water level issue
meaning that when it rains the water from the neighborhood stands in the backyard I am planning a short sale
and i want to add this to the reduction in price
so what is a inexpensive way to fix it and
how can i present this to the lender to show why it is a definite deduction in the land assessment 
You need to have the yard graded to get
the water to the street sewers, if such exist. A more important issue is to keep the water away from the house.
As for cost, I suggest you find reputable grading / landscaping contractors and get some prices. Water / grading problems can be a real nightmare for a homeowner......do it right the first time and be done with it......it beats ending up in court later on down the road.