Zillow, the online real estate data firm, could raise up to $48.5 million through its initial public offering. The Seattle-based company plans to sell about 3.5 million common shares for between $12 and $14 a share, Zillow said in a securities filing. In addition, the company said existing investors, including Technology Crossover Ventures, agreed to purchase up $5.5 million worth of common shares. Citigroup (C) will lead the offering, which is expected to price in July, and Zillow plans to trade on Nasdaq under the ticker symbol Z. As of May, Zillow websites and mobile applications had 22 million unique visitors, representing growth if 102% from a year ago. About 1.7 million homes are viewed on Zillow home devices each day. Zillow uses proprietary valuation models that are automated to give users home values and rental estimates on nearly 100 million U.S. homes. Write to Kerri Panchuk.