Have a detailed lease that everyone must READ and sign so they know what to expect, and then enforce the lease while they live there. 

Now it can be resolved through a long investigation and fact finding and can be undone, but the process to get your property back is long and hard and the our court system and law enforcement is not set up to just kick whoever has your property our or the tenants that are squatting out immediately, so it in essence further victimizes you the real owner as the process draws out.  

Make sure you have a lease in place and that there are no code enforcement violations on the property.

A due on sale clause is enforced at the banks discretion and generally only if they see financial benefit. 

If they are VERY professional, they will have their processes in writing as verification that policies are enforced equally and fairly by their entire staff.6.

The caller said "Hi, I'm from code enforcement..."

I see all Airbnb laws on a spectrum, and many of these cities just fall a little further away from the Denver/primary-residence end of that spectrum; orThe city makes a pragmatic decision to not deal with the headache of enforcing a primary residence rule.

Code Enforcement or the Planning Department should be able to answer those questions easily.

What are my options and how can I enforce them?

We have caps on fee amount of 4.00% total, but I am not sure if a cap is enforced across the industry.