Prove my system wrong!

[Bryan Young]

Looking to have some negatives with my buying, holding System brought up that I might have missed. I am currently buying single family homes in metro Detroit for under $50,000 in good but low income areas. I am staying under $50,000 because I can buy these homes on land contract and have them paid off within 7 years. I won't pay more then 10% down and I also won't buy a house that needs any work. My theory is that my renters will pay off my notes and in less then 7 years I'll own these free and clear. I don't make much cash flow while under contract but I'm also not negative on any. Other the obvious negatives of what if somebody doesn't pay, or repair cost what negatives can you see in my system. So far I have 3 houses under my belt looking to add 5 a year. Thanks