I'm curious about some of the mechanics? 

My plan is to keep my current job as an Industrial mechanic, and invest on the side while still working my full time job.

It causes me a few extra trips a year to reset a breaker, but I have to believe it makes the tenants more prudent about overloading if they know they have to call me to get it reset.Other than resetting the breaker, I can see no other good reason a landlord would allow tenants access to the basement mechanicals. 

Also what would guarantee the partner would get their money out, mechanics lien?

Especially since it’ll help cover your home, autos, and rentals.

I'm a 50 year old Industrial Mechanic, so I can fix just about anything, and my wife is a Industrial Electrician who has went on to get her engineering degree.

With only 1 or 1.5 bathrooms, there is also less mechanical things to go wrong which gives you a lower cost of operation vs. houses with more bathrooms.

No advice on who to choose, but for the applicant who had a few late payments, maybe get 12 checks in advance all post dated for due date or have auto payment from their bank to yours every due date

What I see a lot in your situation is cosigners for each student and one student pays rent with auto pay .

This would be around the better level with best having the owner 100% hands off with notifications and auto reports.