How would you determine the maximum budget for rental properties?

[Vahid Mostafavi]

We are putting together our strategy for rental properties in Houston. We own rentals in Canada but are pretty new to the market in Texas. One question we had, was about the maximum amount spent on a single property. We are mainly interested in single family houses, and we hear from some investors that it is a good idea to buy several properties but spend less than $250k on each. Some others believe that the rent to price ratio is higher for more expensive ($500k) houses. 
my question is, is there any advantage in buying more properties for cheaper price?