Co-Star and Loopnet are the two big sites for commercial real estate. Loopnet is free to search, Co-star is not, but Co-star has far more information than does loopnet, and all of their listings are confirmed as genuine written listings. A large percentage of the listings in Loopnet are pocket listings at best. In many cases they are not even pocket listings wherein the owners of the property don't know they have been entered in Loopnet and may have no intention of selling. Agents enter those "listings in order to get clients. The MLS is primarily residential and has almost no commercial listings. If you are lookings to lease in a particular area, you should drive around that area looking for signs on properties or in windows. Some commercial agents, particularly leasing agents, just rely on large signage on the property, their website and perhaps some advertising, but don't enter the listing anywhere. Drive the area and take notes. If you are an agent, and find a sign on a property, be sure to ask the listing agent if he cooperates. Some don't.