Dallas-area pre-owned home sales sank by 22% in September from a year earlier. It was the fourth month in a row that local home sales have been down since federal home buying incentives ended. Median prices of homes sold in the area rose by 3% from September 2009. But that increase may have more to do with a decline in first-time home sales to buyers using the tax credits. So far in 2010, preowned single-family home sales in North Texas are running 3 percent below where they were a year ago, according to the latest statistics from the Real Estate Center at Texas A&M University and North Texas Real Estate Information Systems.