If the property is expected to be sold in a good/finished condition, there is no discount there.
If the property won't be finished, you can call in your contractor and have him give you an estimate of work/materials needed to finish the property.
You can subtract that amount from the lower end (usually it is a range in pricing) of CMA results.
Often, the amount quoted by the contractor is underestimated - so you might want to subtract 25% more than the contractor's quote.
Hope this helps,
CDPE - Certified Distressed Property Expert
Beachfront Realty, Inc.