Lowest Rent / Price Ratio in the country -- too good to be true?

[Joe Applegate]

Everyone - I NEED INPUT

I ran some statistical analysis and found the cities in the US with the lowest rent to price ratios hovering around 2.0 to 4.0. I then read an article from a prominent investor that he invest in properties that produce a R/P ratio of 8 to 9. 

Are properties that have very low P / R ratios typically poor investments... similar to multifamily units that are producing huge Cash on Cash returns are probably slum units? 

EX: Phoenix, Illinois has a RP ratio of 3.72. The houses are small, very cheap, and rent is VERY high. The city is run down, and not in a good location.... what am I missing here?

Thanks for any input