Aside from giving her general advice and strongly suggesting that she get a protection from abuse order, I stated that I would change the locks but that I would need to be reimbursed for the cost incurred (e.g.locks, extra keys for other tenant, etc.).

This policy was put in place to protect sellers, but if your seller is adamantly opposed to being listed on the MLS, you can't force them.

How can I protect my assets, I am owner occupying a duplex in Middletown, Connecticut.

this is not a protected class, virus or no virus.

Leases are mostly protection for tenants.

If you don’t protect the property, you are almost guaranteed to get termites at some point and they can easily do thousands in damage if untreated.  

Squatters are criminals and not a protected class and the virus has nothing to do with anything. 

I heard that was better geared to people who are investing in larger multi-family.

Lastly, you should review Fair Housing Laws federally and for your state and or city...you can not discriminate against people if they have kids, or because of any protected classes(ie race, age, gender, sexual orientation, etc) I own and manage 37 units for 20 years. 

Dad's credit and rental history is on the line, and he'll want to protect it.