She needs to get with the police to resolve this on her end and get rid of him.

If there is a party and underage drinkers, the police will ask who owns the house and you will be held liable.

Luckily if they do, most courts will give you the unlawful detainer if you request it, and setup another date for a hearing about the monies owed.Unless a judge gives you "immediate possession", the tenants has 10 days to get out from the court date, if they are not gone on the 10th day, you then have to wait 72 hours before filing a Writ with the clerk, which tells the police departments to setup a time to come out and remove anyone from the property.Once you have your writ, you will get a call from the PD to schedule a time to perform the eviction.

I understand how regulations are enforced as opposed to assuming how the fair housing police operate.

Police have even been called. 

I realize state laws are changing around the country, but marijuana is still illegal in MN, and to top it off, he was the one who drove the couple to the unit.After they left the showing, we sent them an email saying that we noticed he was under the influence and we wouldn't feel comfortable approving them as tenants and our landlord would not either (he's a police officer).

Cons: turnover, cleanliness, more police issues, you need to be more active in the community to try to keep your ability to rent clear of town restrictions.  

Finally, check with the city police on crime in that area.  

My brother is a police officer as well.

The risk with section 8 is never really knowing how your local system is policed and if the policing will drastically change with staff or policy changes.