You said mold is growing, which is a clear health and safety issue.

Pets need proper owners or they can be a disaster.

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

This can be as simple as an increase in monthly fees to cover someone's pet project (let's add a pool!)

I'm also checking to make sure no illegal pets or tenants, or waste that will attract pests.

However, if you want to or need to create a W2 income (perhaps for health or retirement benefits) this is one way to go about it. 

The health care industry is also the largest employer in the area.

I confirmed a number of assumptions with a PM company and they thought it should rent easily at 800/mo and allow pets for another 50/mo. 

It's a bit out of my budget but when driving through the town I see it may be a good rental area due to health care occupations. 

This has had no impact on indoor plumbing.Odor is obviously not pleasant, but they are claiming that this is the sole reason they want to break the lease immediately and without penalty and that it violates health/safety codes.