The long-term tenant who stays in one of your OOS-managed portfolio's units for a year, proves him/herself to be respectful and clean, and after a chat is convinced to move into one of your personal portfolio units the next year, while the managed portfolio's unit the tenant just vacated gets the next slob you scrape off the street with a FB-marketplace ad.The ultimate tenant screening mechanism.

Modern floor plans, modern mechanical systems, well insulated, generally separately metered etc.

Does this include mechanicals, plumbing, electrical, structural problems?

Mechanic, Magician, Mindreader. 

If you do them all be prepared and have an upfront screening mechanism like an automated e-mail that says "please fill out the attached application and send us a copy of a free credit report, once we received that we will reachout to you to schedule a showing" otherwise they'll run you ragged. 

I know mortgages & mechanics liens and the like are junior.

This would cover a new roof, A/C condenser, water heater, refrigerator other mechanical items excluding a furnace.

I am a mechanical engineer from Bowling Green and I will be doing my own flips on the side during the beginning of 2017.

But by taking the right precautions and getting professional help, sellers can reduce the inherent risks.The Mechanics of Seller FinancingIn seller financing, the seller takes on the role of the lender.

I found that focusing on the mechanics of the buildings up front has reduced vacancies, repair costs, and simplified my life.