I would send it certified so they have to sign for it. 

Are you a Certified Property Manager?

I’m a 41-year-old father of six who loves the Lord and is driven by a desire to build a better future for my family through real estate.I own a small tile installation business, am a certified insurance agent, and am currently in the process of obtaining my real estate license.

The Notice needs to be sent to each tenant by both proof of delivery required service from the post office as well as by certified mail to the last known address.

Inspections are typically done by licensed professionals like structural engineers, architects, or certified building inspectors.

Are you a Certified Property Manager?

This property has some one-of-a-kind qualities namely a nice creek with inbound and outbound waterfalls at each end of the property (its on a hill w creek canyon).I've gotten the septic scoped and certified, well is good, power needs to be reinstalled as property was abandoned years ago.

They would also give the buyers more confidence as they're a certified and accredited vendor rather than a mason contractor.

The solar system adds no value to my property for rental purposes, and I may even be ripping up the roof & replacing it in the new year.Beyond sending a nasty letter through my attorney via certified mail, demanding the company come pick up their equipment, am I required to take any further action or fulfill any obligations regarding these contracts?

If there are changes you want to make then send your tenants official notice of those changes via in person delivery or certified and regular mail along with a copy of the new lease.