Below is a link from a blog posting from Mike Hambright with Flipnerd.com. I found the first few paragraphs to be very good for those investing or looking to invest into rental properties. After that, the article moves away from what I see with my clients and my own investment portfolio.
The author lists some pros and cons of owning rental properties. He lists self-managing as a con and I got a chuckle when he stated, "I know some really good property managers, and even THEY don't like the management side". It's true, even professional property managers have discouraging days. Another con listed was the influence on changing laws and taxation relative to rental properties.
He also got into financing, but again, what he is describing doesn't fit my clientele as most have under ten rental homes and the others are using cash or commercial financing, which has completely different guidelines.