An STR that is poorly managed may leave the PM without his or her portion of the income, but it may set up the owner to lose the property if that cash flow was needed to pay the mortgage.

That could leave you the emergency fund and money for a good used car.

They are either going to be financially strapped or leave the area, or both.

And many times the owner still has to end up fixing the issue when the tenant leaves. 

If you can leave the property alone and use your funds I would. 

Originally I wanted to do painted concrete, but that would leave the perimeter sticking up.

Do 1 BRRRR per quarter (4 a year, very doable), try to leave as little of your money as possible in each deal, and keep recycling the same money to buy more properties.

For instance, if the neighboring unit has a shut-in chain-smoker, or the house has railroad tracks behind it, it is definitely better to let a lead know and lose them than to not disclose, upset them and lose them (after they leave a nasty review).I'd agree with Jonathan that even late complaints need to be taken seriously, and barring some obvious malfeasance, I would just take the word of the resident and fix the issue.

Rake the leaves, mow the lawn, and water the plants.

You are likely leaving thousands of dollars in tax benefits and cash flow on the table.