That's not a pet problem. 

Tell the tenant that you do not allow pets in freshly renovated units.

Trash was almost a foot deep everywhere, it REEKED of pet urine, rotting food, several full litter boxes, and a dining room literally covered in some sort of... feces... 

Hopefully you have a rental agreement or lease that is solid and has clauses with consequences for unauthorized occupants and unauthorized pets... we charge $50 for each such violation, per person or per pet.

I drove by a "pet cemetery" the other day and it really got me thinking.... lol, sorry.

I would take note when you have access to the property on whether or not it looks or smells of smoke, pets kept on the premises, and any damages you may notice to calculate cost of cleaning fees/replacements.

The problem is lot of rentals don't allow pets which is sad.Can anyone help me to find a small rental home with a small back yard.She qualifies for $1500/month rent.

Also another question, I had a pet deposit with my old tenants.

So I usually say "pets considered depending on size and temperament".

I was going to use the company OxiFresh carpet cleaners they use pet and child safe cleaning products they also have a special for under $200 with the coupon code GR0616.