@Ronnie Howard unfortunately I think by and large most real estate agents aren't investor-friendly, and therefore they have no idea how to market a multi-family property. They are seemingly unaware of their target market and what information an investor needs to properly qualify a property, like rent roll, p&l, who pays what utilities, any outstanding maintenance issues, etc. When clients, like @Kevin Wood, go through their daily searches I have set up for them and see a multi they like, the first thing I almost always have to do is get in touch with the listing agent and try to track down all this information. It's annoying, but it's also part of the value I bring to my clients (thanks for the kind words too Kevin!).
I have often wondered about the owners of these buildings, that they don't think it's important to list with an agent who can effectively market income property and make it easy for a buyer to buy. They really are doing themselves a disservice.
Bottom line, you really should have your own buyer's agent in your corner helping you to gather data and evaluate these properties, especially if you are new.