From what I understand its quite alot when it gets into things like pet agreements or possible lead based paint disclaimers, stuff like that.

No pets?!

a little while later came to find out the tenant was running a pet mill/factory.  

They are tiny houses (all 1/1s) so if its 2 or less people with no pets then I can help.

She lives alone with no pets and we have no idea how it got there. 

When we do our PM WT's we are checking for tenant compliance with the lease (number of people in the house, pets, etc.) and also any obvious areas of concern (leaks, exterior holes in siding, etc.).

I would have to say that it's a pet smell.

Do you allow pets in apartments? 

I’m ISO of Insurance Providers that allow pets and don’t discriminate on dog breed.

Examples: I take a refundable pet deposit instead of a non-refundable one or a monthly fee, I currently pay the whole water bill without taking money from tenants because the duplex is watered together (I will eventually get a separate meter but the outlay is more than I want to pay right now) assuming it doesn't get out of control, paid for the new doorknobs on the bedrooms because the tenants requested locks despite the lead tenant saying they would pay for it, planning to replace the microwave hood simply because it's louder than it should be though it still works, etc.I'm probably losing out on a minimum of $100 monthly.