Karla - Good Thread
I understand what you are looking for in terms of "high cash flow" cities. I assume in the analysis of your data you were comparing median income/values to median rents to determine which cities have the greatest spread.
We call it "warm body" count. the idea being that you need people with income to pay the rent. Our market focus has been - most of Colorado, most of Texas, Northern Florida (Tampa and Orlando and north), both the Carolinas, and a few select pockets in other mid-west cities.
I think however, that you will find that in every market there is potential and as mentioned above, cash flow is a function of the deal more so than the market. Market factors are a function of risk, so that earning a higher cash flow in one area on similar deal points than another area, may involve a greater degree of risk.
Market risk is a much talked about subject on BP but I think that many here do not relate return/risk as a matrix analysis. There seems to be a general sense that all deals have equal risk and as such much emphasis is placed on returns. Earning a 10% return in a great market may be the norm in one area just as earning a 15% return in another are may be the norm. The difference is risk, so your question should really be "what is the least riskiest market?" THEN go make the best deal in that market to earn the highest return.