MAYBE a professional thief can get away with it.

(You didn’t say if they recovered the money)So having watched plenty of thief movies like oceans 11-75 and all the ones involving Sean Connery and Pierce Brosnin, I say GO FOR IT!!

Signs that a property MAY be on septic are: no garbage disposal and/or high water alarm in front yard, back yard, garage.

I have started putting alarms in my sfr's when they go vacant.

How about a smoke alarm chirping?

In addition to what you are thinking about, you MIGHT  need egress windows (every basement bedroom will need one), you may have an issue with light and air (code requirements usually push you to larger windows), fire separations between units, rated unit doors, fire alarm system.It's best to go discuss w/a plan reviewer at inspection services in PVD, but don't expect to get all the answers over the counter, often they can't/won't give a full response until they see the drawings. 

Most of the barn managers we've had boarded a few of their own horses/animals (the crazy light bulb thief had goats in a stall) and rent enough stalls to others to help cover their costs. 

You can get an alarm that calls if the power goes out but this sounds like the pump just stopped working.

If something breaks that line in the picture, you can have it do whatever you want; alarm, phone call, text, warning lights etc.

In addition to checking smoke alarms, fire extinguishers, I also check for plumbing leaks and it also allows me to get the lay of the land on the tenant.