I will provide housing to Intellectually Disabled Adults in the near future.  

I would view a family of 2 adults and 2 kids as preferred tenants over a couple, an uncle and a friend just from the standpoint of wear and tear from multiple adults, stability, etc.

It is a business deal, you signed a contract, they are adults and should just understand that leaving garbage around is unacceptable.

Because it would be 3 adults living in the house I added a price increase to the rent.

My partner suggested I contact them, show them the house, and those that fill out an application will have to fork over $25 per adult for the credit check..and THEN I would reject them based on their eviction history. 

@Rhiannon Then Definitely run a full credit, criminal, eviction check on her and any adult over 18 that will be living there.

If somebody didn't qualify on their own, as a grown adult with their own income and their own references - I didn't want the job of teaching them how to be an adult or to give them their grown-up consequences for being a grown-up adult who didn't act like one in my building.Just say no.  

The unit is roughly 500 sq ft and has two adults & a child living there.

Yes, one reference said, the female's mother was selling her sole rental property, which the couple were living in.

All adults know where they can push the limits.