Then there is the differences in labor costs for different work, and of course time charting.

Don't cut it so close you can't sleep at night.You may be able to get the 3-unit under contract with a contingency of selling your flip, but that will probably make your offer less competitive.Otherwise, I would wait until you at least have your flip under contract (and have a more precise expectation of net proceeds) before going shopping again.The 3-unit property is not a one-in-a-million opportunity that just happened to pop up right now. 

One might expect Chipotle which is a growth stock to perform better than Microsoft a good old reliable blue chipper, but the 1 year chart shows a massive out performance by MSFT.Risk, and risk tolerance are probably the most overlooked aspects of any type of investing.

If someone wanted to do a chart with those 3 along the top, and rows downward for what you do/don't get with each, that would be super awesome. 

I liked the comprehensive review of on-line Property Management services (showing the fees) offered on AccidentalRental.com - specifically the chart comparing features of:  Cozy, Rentulations, Tenant Cloud, and turbotenant. 

But, you really need to know the fine details in order to put yourself in a safe financial situation based on precise location selection.

Fannie Mae does not specify the precise documentation the lender must obtain to verify that a non–U.S. citizen borrower is legally present in the United States.

You want to be there at the moment they are ready, and that means multiple mailings, to arrive at the precise moment that selling fills their mind.

In fact, all of the other scenarios you explained are precisely why I want to avoid commercial lending for now, although I do see how they could be helpful in the future.

But that requires you to be precise about your assumptions including the discount rate.