Residential real estate is becoming a sellers' market, the Des Moines Area Association of Realtors said today with the release of pending sales in March that showed double-digit growth from February and a year ago. Contracts were written to sell 1,176 houses last month, an increase of 295 from the same time last year, according to a news release. Buyers closed on 779 sales in March. There were 3,852 active listings, down from by 677 listings a year ago.