Being able to rent out your property is part of your bundle of rights as a home owner. You don't need a "landlord license" to lease your own property; however depending on what type of property you are trying to rent and in what manner, you may need a special license.
To get started answer these two questions: What type of property are you renting? and How long are you renting it for?
Special licenses are required for properties that are renting with short-term leases (for Sandy I believe it is less than 30-days). This most likely would apply to "ski rental" properties or similar type rentals that are leased at a nightly rate for a few days at a time. If your property resides in a condo or a PUD the HOA may have restrictions on the number of rental properties located in the project and cars, # of occupants, etc. I just completed an appraisal on a property in Cottonwood Heights with a rental license from the city because it was being used as a Ski Rental.
Renting is a great way to go! Remember to make every agreement in writing and be very specific of what each party of the agreement is expected to do, pay, repair, and NOT do, pay or repair. Clear all that out up front and you'll be a happy landlord. If you have more questions call me anytime! As an appraiser and agent I work with this kind of stuff on a daily basis. GOOD LUCK!