I had a condo before marraige. We bought a house and rented the condo for 6 years.
As I recall, you declare the rental as income and choose a method to 'depreciate' the property (either over a set period or all at once). Read the rules as I can't remember the details.
However, the CATCH on rental property is this: When you sell the property you will have to pay taxes on the profit from the sales unless you use the profit to buy another rental property. Example: you bought the home for $100,000. You rent it for awhile but sell for $150,000. You pay taxes on the $50,000 at your current bracket (probably ~20%). This is $10,000!! Only by using the $50,000 for a down payment on another rental can you avoid paying so much.
What we did: We sold our rental and bit the bullet on the taxes. Our profit was enough to buy an undeveloped 5-acre in the country (no water, no power, dirt roads) plus a camper to use for a little 'house'. About $5,000 went to taxes
We have been saving successfully for 5 years to build a modular on the land in the next couple years.
Hope this info helps.