I could have put security measures in place during the previous renters' stay, but I've no doubt they would have made good on their threats to stab me in the back, etc.

It is not a measure of your quality of character if you do not naturally know how to be a good landlord the second you hand over the cashier's check to buy your first investment property.

Wealth is not measured “just” in $, is it worth that $ to give up that time. 

It's their fault, and the power lies with them to reverse their poor past choices and pick themselves up a bit by their own bootstraps.You're going to tell these new tenants that what's primarily wrong with them is not a legacy of a crime against humanity in the form of three hundred years of black slavery, followed by an unfunded emancipation that turned a huge number of Americans into desperate economic refugees based on the color of their skin, followed by a legacy of organized race hatred, bigotry, pseudoscientific and religious condemnation, and of course overwhelming and widespread intimidation and coercion, followed by a series of failed half-hearted half-measures coupled with an absolute refusal to consider slave reparations and the most lopsided minority levels of poverty and incarceration in the developed world.You're going to explain to these black folks that all that is of secondary importance, and what's REALLY important now is that they get better managing their money so they can hand it over to you more efficiently and you won't have to work so hard to get it.

That said, cap rate isn’t a measure of deal quality.

The pad measures 24 feet by 32 feet. 

As with any big decision, measure twice cut once.

Worst case scenario, if he comes back and want his deposit back and makes you go to court, then you have to measure if is worth your time or not. 

But you may have other goals or standards with which you will have to measure this deal.150 a door?

If you google ROI, you will find that it is defined as some measure of periodic return or income relative to the initial investment that generates the return (usually measured annually).