If you do what you are thinking of, it will probably ruin you financially.Go out and invest in real estate.  

That what's going to happen is police involvement and a court eviction that will ruin their credit (hopefully that's true or something like it where you live). 

However, that being said, in EVERY scenario where the tenant had a pet (dog or cat), we found a lot more damage than normal wear and tear (horrible smells, ruined  or scratched carpet, pee smell in the wood flooring that was impossible to get rid of, etc).  

Being that one of the tenants is a professional I doubt he would allow anything to happen that would ruin his name and credibility.

Our properties are 2 and 3 stories (~3K sq ft) and dogs pretty much stink / ruin floors however, responsible pet owners willing to pay fees typically have been good long term tenants.  

Before you get the police involved think about whether you want to potentially ruin someone's life over doing a recreational drug in the privacy of his own home.

., ruin your bottom line?  

No .. we provide all our tenants with a binder on their home which contains copies of all manuals for the appliances and call lists for all our service providers.All our laundry units are in catch trays with floor drains ... so no ruined floors.And, according to your math, the tenants "pay" for the unit over 3 years. 

Dont let that cancer infect the other tenant.

However, I know I wasn't going to ruin my credit now was she even though things got very uncomfortable.