CoStar Group (CSGP) began offering 3.75 million common shares of the company's stock Monday to fund an acquisition that will make CoStar a one-stop shop for street-level commercial real estate. In April, CoStar announced plans to take over LoopNet Inc. (LOOP), an online listing space for commercial real estate properties. Washington, D.C.-based CoStar currently operates a database of commercial real estate research and analytics, which includes occupied CRE properties. Through the $860 million acquisition, CoStar will have extensive coverage of property values, market conditions, available real estate and other economic data concerning the CRE space. The firm began offering shares Monday, with JPMorgan Securities as the sole book-running manager. Needham & Co., Stephens Inc., William Blair & Co. and JMP Securities are co-managers. CoStar expects to grant the underwriters a 30-day option to purchase up to an additional 562,500 shares. The offering is not conditioned on the closing of the LoopNet acquisition, CoStar noted. Earlier this year, CoStar sold the building it used for its Washington, D.C. headquarters, earning almost 150% return. In the first quarter, the company earned $15.4 million. Write to Christine Ricciardi. Follow her on Twitter @HWnewbieCR.