Real estate website Zillow will buy competitor Trulia for $3.5 billion in stock, but Realtors shouldn't be too concerned about the combined company hurting business, said Tim Rood, a former Fannie Mae executive who is now partner and managing director of Collingwood Group. 

"Realtors, they're independent contractors. They just want to win more customers. So if Zillow wants to spend all of its money advertising and Realtors can get more targeted, pre-qualified buyers, they're perfectly happy," Rood said in an interview with CNBC's "Street Signs."