Take ownership of your mistake and learn to do the proper due diligence recommended above😊

I recommend learning a bit on how to read the financials, but find yourself a great Accountant to help you analyze the financials and tax returns to make sure things make sense and are proper. 

My systems are ok, rather I have to give credit to the individuals I work with as well as proper tenant screening.

Screwing a 4x4 screen into a roof would probably not show up as an "installation". 

I’ll try to answer some of your questionsonce a note has matured the note holder has the legal right to call the note due - with proper notification to the debtor.  

. - Agreed, sounds like you don't have the time to properly vet candidates.

So we went directly to Lowe’s, who provided a receipt for microwave, installation, taxes, etc. totaling about $530.

Operations- tenants refusals, either cull them before they get to you by requiring autopay as an example, document on their application why you refused them, make sure your facilities are maintained properly and no safety hazards exist, etcLLC.

You were upfront about there being no vent and needing to use a ventless option, so you don't have to install that for them or even split it, but splitting it probably is somewhat fair. 

:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.