The most homes I owned at one time was 42. Although I prefer flipping, I do own some property. In my opinion, positive cash flow is often arrived at with what I like to call "perfect math". I do not believe in making a living off of rentals that have mortgages on them. I have learned this through the years from not only my experiences, but also through many of my friends with rentals.
The best way to really make a living off of rentals is to buy in less than desirable areas, pay cash, and make sure they have a lot of bedrooms for big rental payments from the governments section 8 program.
Example A. My first rental was a 2 unit, paid 76k and made about 200 per month cash flow in a perfect world. A couple repairs and a month of vacancy later, all of my cash flow was gone for the year!!!
Example B. A close friend of mine bought a home for 9k, put about 9k into rehab. so he is all in for 18k. No mortgage, and made it into a 7 bedroom 3 bath cash cow! He is getting a section 8 check every month for around 1200 bucks!!! And the tenants pay all utilities, even water!
I am sure I will have a ton of folks on here telling me I am wrong, but it is what works for me. If you want to talk further PM me, and I can pass you the BP member that I used in example B.