I agree with the idea of letting them stay, adding the pet deposit and socking the money away because in the end, this can be a challenge to take care of the odor.On the other hand, if the contractor is not used to cats even one dirty litter box can cause a significant ammonia odor (cats consume a very high protein diet and thus produce a high urea content urine).  

I would also contact the local Sec 8 office about the possible drug use.

this guy was into some funny business...you may find drugs hidden behind walls or in the attic..."...and the mirrored ceiling got the most attention.Oh, there was also a seven foot long aquarium in the same wood trim dividing the foyer and the kitchen but that was removed.I have considered removing the ceiling and just go back to regular sheetrock. 

Examples could be pre-foreclosure, tax lien, loss of job, death in the house/family, divorce, high medical bills, drugs, rental property gone bad, or anyone that was diagnosed with a severe medical condition.

I have a degree and post graduate work at Yale, I do not drink or do drugs, BTW, I was simply over qualified for what was available. 

Drugs aren't any worse there than any other south Texas city.

Maybe the original owner didn't mind having a felony drug dealer live at the property but you might.

At the very least, this tenant is possibly on drugs and I think she's sort of a "risk" for trashing her own house before she leaves if she's unhappy about being forced out. 

Now one of them told us that he has a misdemeanor in 2013 for drug possession.  

Lights on, tv on, heat or a.c. on.The other half of the time I get a call from someone who just came into town or I give them a drug screen in the morning to get into the refinery.