$100 a door doesn't help cover the unexpected repairs. 

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases: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.

Estimated cost for remaining changes (all new electric, drywall, tile, fixtures, cabinets, roof, doors, windows, heat pump, some siding, and fencing.

You will want to consult with a lawyer.In regards to your last two questions here's some background on what makes a contract valid and enforceable:Offer: A promise to do or not do something within a certain time period Acceptance: A clear and direct statement that all terms and responsibilities are accepted Consideration: A legal and adequate inducement given in exchange for the promise Capacity: The parties to the contract must have the legal capacity and competency to contract Awareness: A party must be aware of the contract Legality: The contract must be legal in the jurisdiction it will be operating in***Not legal advice*** Steps I would take: -Review contract in detail to understand each counterparties responsibilities (if you are not aware)- Email a copy of the lease to each of the tenants listed on the lease and reiterate lease expectations for termination notice, rent payment etc. - If the lease was signed via Docusign (other esign may have same ability) - you can go to the envelope, go to history and view the IP addresses for each action taken.

When we built up the triplex, we set it up so that each of the 11 rooms can be rented out individually (all BR, except 2, have their own bathroom behind an electronically locked door).

I can't see how some investors cashflow just $100 per door in some markets. 

How about a house with an ADU, or a basement with a private entrance that can be rented out?

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases: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.

I would warn you though as soon as you give an inch, the next month if rent is not paid on time you may have opened up a door of forgiveness that was not intentional.

Should I buy up as many cash flowing/appreciating properties for long term holds as possible to add doors to my portfolio (although, I haven't enjoyed being a landlord thus far...)?