This is actually pretty common in the apartment industry and some apartments will even give you, as the renter, the option to pay the rent until they re-rent it or pay a fee and not have to worry about them re-renting.

I have an insurance policy (in my LLC name) for each property.I was wondering if this is common, or is it better to have one Umbrella-type policy that includes all the properties, so insteadt of having to get a new house added to my existing policy, I would be able to just add a new house to an "umbrella policy"Thanks!

RUBS is likely the most common when looking at larger scale complexes. 

More frequent cleaning of common spaces? 

Cold calling some multifamily owners, I begin to face the "I've been lowballed before" objection a lot. Tips to overcome that? 

Sales comparison is the most common for residential.

I’m choosing to be aware of life around me, and to embrace the situation that has been presented.

The two most common options are to treat yourself as an employee with wages or to treat yourself as an LLC member and receive a distribution from the profits.Choose Not to Receive Payments. 

Per this article from a couple years ago, it sounds like most renters insurance covers their animals and damage their animal may do to person or property, but you need to confirm that have it to protect yourself.And as @John Lenhart mentioned, adding rules and fees to keep common areas clean and tidy are well worth it.

Cat allergies are generally more common/severe, and the urine can ruin a place.