Each has it's own internal policies and procedures, each has it's differing level of cooperation with housing providers. 

Non-payment of rentBreaking lease earlyAdding unauthorized tenants or animalsThose are probably my most common three, but they aren't much of a problem since I have policies and procedures in place to handle them quickly and professionally.

Prorate all rents accordingly and let them know the move out procedure. 

One CNA, one dental hygienist, another IT guy and a graduate student, all pretty good.

After the pups are gone do an inspection and charge tenant for all repairs, that is normal procedure for all tenant caused damage.

If it comes back to you, just keep it unopened.But, if you don't do it, they usually have a year under the statute of limitations to sue you for not following the procedure correctly.  

As your portfolio grows it will become too complicated to keep up with all the different terms and conditions if you don't stick to a Standard Operating Procedure.

I never sue in small claims court, landlords don't respond well when they aren't forced to pay a lawyer (small claims relaxes the procedures and lawyers are not often necessary.) 

And if you have  lease, then, you have to evict and go through the eviction procedures.  

The biggest takeaway that I found is that you need to start implementing policies and procedures into your business now to make these types of (unavoidable) situations easier to deal with in the future.