I am not against agents in any way, especially for housing, but there really is no comparison between commercial and residential agents and deals. The commercial ones I've dealt with care most about getting the deal done and protecting their own arses in the process. Most residential agents are looking out for the client first and closing the deal second and almost none of the deals are dual representation (like a lot of commercial deals). All I'm saying is do your due diligence yourself and don't rely on what a commercial agent, that has skin in the game, tells you about the market. I would do a commercial deal without an agent, but I wouldn't do one without an experienced commercial real estate lawyer.
Do a search on
www.loopnet.com for similar commercial properties in your area, both for sale and lease. It's a little limited unless you pay but you can still get a pretty good sense of what's for sale and for how much in your area for free.