Here's a quote from Google on search topic "ozone removes odors":An ozone generator will not only remove pet odors but other troublesome odors caused by mold and mildew, fire, water damage and others.

Be wary of dogs of all kinds even if they seem friendly do not pet them.

We also replaced the plywood in several spots where the pet urine had saturated the floor. this has really helped.Michael

Have a minimum age restriction, get a photo ID from renters, get a security deposit, have an exterior camera to monitor for too many people or unauthorized pets etc.We keep taking most of our profits to make upgrades to the property, but house does pay for it self so we have a free Lake house!

I'm considering asking guests with pets to leave a $10 cash pet fee on the counter and explain that it's for the cleaning lady.

On time for appointmentBROUGHT NECESSARY ITEMS: Identification, application information, references, application fee, holding deposit...Filled out application completely and truthfullyAble to verify all of the necessary informationAble to pay full amount of rent and depositSufficient monthly income of 3 times the rental amountVerifiable income and employmentStable income or employment for a minimum of _____ monthsFinancial obligation of no more than _____% of incomeSatisfactory credit history (no bankruptcy)Provided credit referencesAt current address for a minimum of ______monthsGave proper notice to current landlordGave proper notice to previous landlordNo prior evictionsNo problems with previous landlordsDeposit fully returned (none withheld for damages)No complaints or police reports regarding disturbing the peace, etc.No significant violations of a previous rental agreementNo pets or is willing to sign a pet agreement and meets additional pet criteriaNon-smokersHas a Delinquency Rate less than 45% based on Credit Score Analysis performed by Tenant Background Search.Has a credit grade of B or credit score of 620 or higher per Tenant Background Search.

There is a product called OdorXit AQM which I used successfully in a unit which was very badly assaulted with pet urine. 

Other common lease violations are damaging the real property, staying longer than agreed upon, keeping pets without the consent of the owner, or breaching one of the material terms of the lease agreement.Performing illegal activityInvolvement in an illegal activity may be valid ground to evict a tenant.

We don't allow pet dogs, or credit scores below 600. 

House Rules: In the event that the premises are in a building containing more than one unit, Lessee agrees to abide by any and all house rules, whether promulgated before or after the execution hereof, including, but not limited to, rules with respect to noise, odors, disposal of refuse, pets, parking, and use of common areas.7.