The reduction in mechanicals allows for a quieter and lower maintenance home, and the building method also creates healthier air for the occupants(great for people with breathing issues like asthma.)MG

. :-) Or play Columbo...Do as @Scott Weaner says and change the mechanism so she needs to use a key to lock the door.Watch the property and do your periodic inspections.

I am a 20-year old studying mechanical engineering at the University of Miami. 

Can someone describe the mechanics in detail?

I had a tenant ask to install their own clothes washer because the husband was a mechanic and they wanted something heavy duty.

when the mechanic tells you why you thin thank goodness, and then bang your head on the wall and think, "duh".

They then have the landlord fill out a voucher where you will detail who pays which utilities and how your mechanical are configured. ie. nat gas steam heat vs. heating oil on a force hot air system.  

These are wholesaling and retailing--you'll find a lot of info about these strategies and the pros and cons here.There's a sort of "in between" strategy, too, commonly called pre-habbing, where you do only the major work (mechanics etc) and sell for a higher percentage of value to an investor who can finish the work.IN GENERAL, assuming that you bought the property "right" and can get the work done correctly and at a reasonable cost, pre-habbing and retailing will be more lucrative on a per-deal basis.

That's the mechanism for avoiding unlicensed brokering.

These are mechanical things that can be done with a dose of common sense, made easy with some youtube video and online forums.