Professional Property Management Value as a Function of Monthly Rent?

[Mike M.]

My basic question is this:

For those with multiple properties that span a wide rent range (here in Texas, $450/mo will get you a 2/1 in a blue collar area; $1300/mo will get you a 3/2 in a mature, stable neighborhood), is there a "law of diminishing returns" aspect to outsourced property management as rent (and supposedly tenant quality) goes up? This assumes that professional property management costs do not vary as a function of rent (I'll find that out tomorrow when I start calling around). If they don't vary as a function of rent, what is the community's experience with squeezing the most value out of professional property management in terms of monthly rental income?

For background, I've got good, stable W-2 income, and looking for long-term appreciation out of my investment properties, not necessarily huge cash flow. However, I won't ignore a good cash-flow deal, even if the appreciation prospects are less. I've been running some numbers on a couple different leads from my direct mail campaign, and property management costs appear to sink one that meets my primary investment objectives (potential rent of $1300/mo). I don't mind managing a couple higher quality tenants, but I'd also like each investment to stand on its own with professional management built in.

Thanks in advance for your comments. I don't want to ignore the numbers, but also lack the context at this point in my RE career to reconcile these numbers with real world experience.