Is the cost of installing any equipment and constant monitoring worth reducing occasional infractions? 

Those fines are not for minor infractions, they were probably in violation of key parts of regulatory requirements and repeated several times along with other minor infractions.

She got rid of pet so she's complying, and I wouldn't change a thing, if you see the pet in the future, you can choose to give her a lease infraction notice and or termination.

Most infractions happen due to a neighbor notifying DC. 

Additionally, you need to know if the water company found code infractions or are they just referring to the one issue of a gate valve missing? 

As Matt mentioned, a Realtor or licensee can act unethically which can translate into infractions of the law.Licensees are seen as the expert in the room, they may not be but the license demonstrates a greater knowledge than the general public.All professional licenses are based on protecting the public from unqualified actors in business.

Has anyone invested in fractional equity investments and what was your experience?

These are the renters that cause death by a thousand cuts, small infractions or problems but the sheer volume becomes a regular irritant.They constantly complain about "problems" like mold in the corner of their tub that could easily be cleaned or that the neighbor's porch light is too bright and shines right into their bedroomHabitually late with rent.

Long-story-short, I had a house meeting with everyone and signed extra contracts stating that any further infractions were grounds for not renewing their lease the following month.  

Yes Chris, that's what I'm saying and not so gleefully about it, the real trick is cover the big stuff and when you have a small infraction do an on the spot correction or take immediate action to cure the issue, then they may not write you up as badly as they might have. :)