Difference between Residential and Commercial Property Management

[Matt Sullivan]

My wife and I currently own a small residential property management firm and would like to expand in the future.  One area of expansion would be into the Apartment and Commercial Building Management.  Of course I want to do my due diligence before jumping in to something I don't know.  Can someone explain the differences between Residential and Commercial Property Management, and maybe have a resource (book, blog, etc) that they recommend to learn more?