Newbie question on creating money in real estate.

[Richard Lunt II]

This may sound like a very basic question relative to investing in real estate. I am 47 and will be retiring from law enforcement after a 25 year career and I will be starting my search for my first investment property. I have been listening to Bigger Pockets for about a month as well as reading some real estate books. My desire is in multi-unit properties and I understand the possibilities of gaining profits through appreciation and positive cash flow. I am just not quite understanding how individuals say they make "income" on their properties. Any information would be appreciated. 

[Sam Levin]

Also, thank you for making a career of protecting your fellow citizens. I hope your retirement treats you well.