Ok, thought experiment with some made up numbers that I think are legit.
Say you buy a $200,000 house, paying 20% down ($40,000).
Mortgage is $160,000. Let's say 5% interest and to be conservative just keep it that way throughout the year ($8,000/year, $667/month).
Most halfway decent rental properties will get at least 0.7% rent compared to the price of the house. So rent is $1,400/month.
I've heard property managers typically work at 1% of rent collected. Let's be conservative again and say 2% = $28/month.
So you're bringing in $1,400 (rent) - mortgage interest ($667) - property management ($28) = $705/month. Over the course of a year that's $8,460.
What is a normal repair budget for a year? $3,000 to fix just the necessary stuff? So $5,460 you take home per year. That's on $40,000 you put down.
ROI for the year: 13.65%
Now you might say, the mortgage is going to be bigger cause you're making principal payments on top of the interest. That's true, but that's not money that goes away. It is just getting reinvested into the property itself in the form of equity. Sure, the property might not appreciate but stocks might not either so that's a wash in my book. Both tend to go up over the long term if you pick wisely.