This means around the 1st of the year there is a temporary boom of unqualified renters entering the market and to make matters worse the temperature normally drops tremendously which increases the danger of frozen pipes or high utility bills (choose one or the other) insurance agents tend to frown upon vacancies... 

Knowing that once you cross north of 5th St. you need to increase your vacancy credit by 1% will have a much larger impact on your true returns than using MIRR vice IRR.The nearest I can figure why MIRR doesn't get more traction on BP is that most people don't really understand IRR beyond the definition "the rate that sets the NPV of future cash flows to zero", so the factors that you pointed out don't make sense.

Would you prefer an ongoing 20% ROI, while not expecting any increase in the value of your original outlay, or, would you settle for an ongoing 10% ROI, while counting on (uncertain) future appreciation that might compensate you for the other 10% that you could have been getting from day one?

Increase earnest money.

I take their financials into consideration when determining if I can find ways to reduce operating expenses and increase my bottom line.

They are currently paying $450 a month in rent and have not received an increase in their history. 

With rates moving higher, it is likely that your rate will increase in the future. 

Short increases the chances of a return call but being too vague decreasing the chances. 

Yeah focus on increasing your day job income, advancing in your career and keep an eye on the big picture.

Can you hire a helper or two to handle the actual mowing while you work on increasing the number of clientele you're serving.3.