I use Concrobium from Lowes because it seems to work and doesn't have an off-putting odor.

Pictures are shown below but the one thing that is missing from the photos is the putrid smell of cat urine and feces (along with other odors too).  

Contact a local odor removal service and have them come over to analyze and recommend the best method for remediation.

You are responsible for the safety and health issues in your building, and hoarding and odors like you describe are health issues (think rats) for the entire building. 

I'd like to avoid anything that would make it unpleasant to live there (odors, damage) whereas we're fine with "preference" items like countertops, flooring, paint. 

I was hoping she would grumble about the rent increase and being held accountable to the due date.

The other unit smells heavily of Kilz spray which has been used to cover up previous pet odors, but I'm hoping this can be ventilated.About the owner: He is 74 yrs old, wanting to retire...

We have been sick since we moved in the apt upstairs and we told you there was mold in the stairway where the airconditioner unit is... we smelled a musty odor in the stairway and thought it may have been the rug and asked if we could remove the rug.

Stinky garbage disposal - are you aware that without proper and ongoing cleaning garbage disposals can emit a foul odor.

These rules shall apply to, but are not limited to, noise, odors, disposal of trash, pets, parking, use of common areas, and storage of toys, bicycles, tools, and other personal items (including signs and laundry), which must be kept inside and out of view.