Hi Victor. Thanks for your post. Though we have not met, I know you are thought well of in the Knoxville area. With that said, I will have to disagree with what you have assumed (though you were limited to only the few scraps of info I have posted).
These properties are not in Knoxville or even the Knox metro area and thus have a significantly different market. A nice 3 bed home in Knoxville may rent for as much as $1200, in this area a 3 bed in a good neighborhood is a round $700-750. Extras and improvements may push for a higher rent, but not enough to really justify them. This happens to be in a small town where property is cheaper and so is rent (though properties are generally far more than 35k each). Do these lower prices mean that this is a town of solely D class properties? Hardly. The rules for Knoxville and the rules for there aren't interchangeable. If you tried, I can go ahead and tell you that your bank account isn't going to be happy.
I actually had a property in the Knox area like what you described, and ultimately sold it for a small profit and decided that low C-class and D class property wasn't for me. While some people like those properties, I find that I prefer my passive income to be a bit more passive.