Two points of view here. One is self manage and two is outsource the service. Both are viable choices and realy depend on the individual investor and the investor's geographical location to the investment.
I live in CA. Do you think I can buy sfr's here and have positive cash flow? The answer is very rarely or more accurately, a needle in a haystack!
Therefore, I must invest out of state, and since my state is so large, out of state means hundreds and in my case, a couple thousand miles away. I can certainly answer phone calls and hire service providers to do misc. rpairs, etc., but how do I confirm the job was done right, that I was not charged for itmes that were not completed or necessary? I need someone on the ground to protect my interest.
Now that brings up the discussion of "how do you trust your PM?"
Well, jsut like everything else, that takes time, effort, and you have to stay on top of them as well. Having the right team memebrs is crucial and knowing how to interview and hire them is just as important.