Depending on the neighborhood and time of year, that number may fluctuate up/down. 

However I did start with buy and hold myself almost 30 years ago, and I accumulated 16 multi-family properties in 18 months, with owner financing or bank financing (portfolio lenders,) but the problem was I did not have a good reserve of funds and the fluctuations of incoming rents was stressful.As far as finding properties, the properties you need to locate for wholesaling, buy and hold or fix and flip should be properties priced below market, which might need work.

It was an old converted building that was never sub-metered.The only bill that seemed to seriously fluctuate was the water bill.  

People's credit scores fluctuate over time.

Make sure showers are getting enough hot water and the temperature doesnt fluctuate. 

My credit score is still fluctuating between 690 - 705.

Plymouth and Ann Arbor "fluttered", but as long as you were not forced to sell, you were fine...actually more than fine.The cash flow being positive allows the REI to still profit during those times of flux...whether they are large or small spreads in that fluctuation. 

I would not want to pay and recoup a fluctuating amount each month.  

Like Brian Gibbons points out, you are also playing with the fact that prices/values might fluctuate that far out. 

Home prices have fluctuated as much as 30% from peak to valley.