This is an investment as old as the practice of land ownership. 

Ideally, the landlord charges enough rent to cover all of the aforementioned costs. A landlord may also charge more in order to produce a monthly profit, but the most common strategy is to be patient and only charge enough rent to cover expenses until the mortgage has been paid, at which time the majority of the rent becomes profit. 

Furthermore, the property may also have appreciated in value over the course of the mortgage, leaving the landlord with a more valuable asset. 

According to the U.S. Census Bureau, real estate has consistently increased in value from 1940 to 2006, then proceeded to dip and rebound from 2008 to 2010 and has been increasing overall.

There are, of course, blemishes on the face of what seems like an ideal investment. You can end up with a bad tenant who damages the property or, worse still, end up having no tenant at all. 

This leaves you with a negative monthly cash flow, meaning that you might have to scramble to cover your mortgage payments. 

There is also the matter of finding the right property. You will want to pick an area where vacancy rates are low and choose a place that people will want to rent.

Perhaps the biggest difference between a rental property and other investments is the amount of time and work you have to devote to maintaining your investment.

When you buy a stock, it simply sits in your brokerage account and, hopefully, increases in value. If you invest in a rental property, there are many responsibilities that come along with being a landlord. 

When the furnace stops working in the middle of the night, it's you who gets the phone call. If you don't mind handyman work, this may not bother you; otherwise, a professional property manager would be glad to take the problem off your hands, for a price, of course.