I'll post my simpleton "first step towards success" story.
In 2015 I bought a rental for 135k, took about 28k in traditional down payment along with fees. My mortgage is $670 and rent is $1300, so a spread of +$630 every month. I have a home warranty for $500 a year so no problem is over $75. When the hot water heater failed, it costs me a grand total of $75 to have it replaced. More than makes up for the yearly home warranty cost. I bought the property with a new roof, new flooring, and new appliances, vastly reducing my upkeep.
At the time of purchase I was finishing up my undergrad, and I'm currently 4 months away from becoming a PA, with an expected annual salary of 90-100k. The rental income since I bought the property has allowed me to stay out of debt while in school so add that to whatever ROI and COC formula you have.
Wifey and I have a plan for once we switch from a one income to a two income household, with a big part of that plan being to purchase more rentals. I'm not really looking to flip, I'm not into hard money, I'm more slow and steady. I still invest in a Roth and in some mutual funds.
One of the things that motivates me is when a 40 hour a week blue collar worker dies, their income stops and their kids are left with a usual small inheritance and that's it. If I'm able to continue to purchase income producing real estate, my kids can enjoy income in the future. Not everyone's cup of tea, but I like the taste.