I went high on the expenses, which came to roughly over $20K. assuming 1 unit to be vacant per year (83.3% occupancy).

The calculator estimates that operating expenses are equal to 50% of the monthly income.  50% is a rough guide. 

It's not your fault that the tenant has to vacate, so the tenant should have insurance to protect them against any additional expenses.

We require a minimum credit score of 620 (averaged between occupants) to qualify.

Cash-flow is for "keeping the lights on" as in covering operational expenses to defend against any need for additional capital investment. 

Text isn't an officially acceptable way of relaying this information here.On the somewhat rare occasion when I deduct from a security deposit, I send an itemized list of the expenses deducted to the tenant's new address via certified mail. 

i have 4 STRs that i use professional PM, 2 of the STRs, after expenses including PM, are not outproducing my LTRs.For optimal ROI in this market requires a value add and quick, at least partial, exit.

This reduces exit options and affects the value. 10) Small number of small units is the most expensive residential development there is.

Our next big objective is to eliminate our housing expenses by purchasing a triplex or fourplex using my VA benefits.

They are not that expensive, and you can easily do it by yourself.