What's the cash-flow after expenses?

This hidden cost significantly increased my loan’s overall expense, and I only realized it after reviewing the final terms.

The paid version for sales has a lot more is not crazy expensive for a SaaS.

But ya have to make some educated prognostications in life.Add this to the information your processing - What your talking about doing is eliminating around $4000 or interest expense (which is deductible anyway so really could be a real impact of eliminating $2800 or so) of debt in exchange for paying over $10K in capital gains tax (don't forget possible state gains tax as well).  

The first round of tenants we got paid the same rent as before and also paid their own heat and electric. 

We put this in our offers to differentiate ourselves from other offers and we can write off this expense as a tax deduction.

Despite this, they placed a tenant with a 530 credit score, who paid one month’s rent (FPM collected their 50% commission) and the tenant never paid again.

This investment should have done very well based on these facts, but the biggest drag on performance was the yearly high "unexpected" property tax expense ($300-500k drag on NI per year).

So why would you pay what they paid then? 

Since you estimate a resale value of $200-215K and renovation costs of $60-70K (although you said that's on the higher end), your margin is tight, especially considering closing costs, realtor fees, and unexpected expenses.