Is there an odor?

Yes, pets caused the odor and we had to have that treated,  so gross.I am 100% sure that he's not getting his damage deposit back, nor the non-refundable pet deposit.  

The dog odor was awful, carpets disgusting, bathtubs filthy, etc. 

I mean, a Home, Retail Store, Animal Hospital, Nail Salon, or many things would be great beside of our building as they do not produce foul gasses, odors, and vibrating our building for hours a week.

if they grumble at a potential customer to kick them out, you've lost a customer, if they let them look around, you've lost a customer..

So he collects less rent for the insurance office, but his expenses are correspondingly lower.Oh, be ready for residential tenant complaints upstairs when you have restaurants or delis downstairs, particularly odors and noise, especially if they open late.

They work wonders on neutralizing tough odors like pets and smoke.  

What I suspect is that it is a 3 bedroom system (main house has 3 bedrooms) and that somewhere along the way the 4th bedroom (studio apartment) was illegally connected to it, overloading the system causing excessive odor and runoff.

Morale of the post, be prepared to go very deep in any strategy that may have an odor about it convincing others to follow some avenue to make their first million.  

I had some tenants never let their dogs out for months and the odor was incredible!