The current tenants seem nice, but during a visit to the house for reasons unrelated to the tenants, I realized they had two adults living there who were not on the lease (one of the tenants' parents, I think).

I told her the home was for adults only, and she should move elsewhere.

Students, I could understand them going home for the holiday season, but working adults was a bit harder to understand.

If it rents in two months, you've earned a bonus.This may sound like a harsh penalty but this is what "adulting" looks like.

Even Adults like a soak once in a while.

A lot of people do actually have parents moving in with them or adult children who haven't quite flown the coop, and yes, some people actually do have or want live in nannies.  

For individual adults who are each responsible for the property and payment, send an individual letter to each one.

I'm 44 years old and have spent my entire adult life in construction and/or engineering.

So that means I'm on the edge of being that boring housewife with two adult children who have separate lives of their own to live...

I'm not looking for legal advice from this forum and will escalate this to my attorney if necessary.I'm currently under contract to purchase a fourplex and during my due diligence I have determined that one of the apartments has an additional adult living there who is not on the lease.