Most of my adult life was spent working as a Firefighter/Paramedic.

One question is liability and insurance, also what if the 'adults' (ie couple on the lease) leave and all that remain are the students? 

For example, I mention that every adult must pay a $30 application fee, pass my credit/criminal background, make a combined income of 3x the rent, and whether or not the property accepts pets.

They need to be adults.

Know that children are rough on properties versus older adults with no kids.  

However, the price is the same per adult (ages 16+) whether or not you’re attending the content.

At some point she will get tired of her adult son taking advantage of her and you will be stuck.

I'd probably call Adult Protective Services and report the issue.

If all adults are screened, you can avoid potential legal issues down the road, especially in cases where one occupant engages in illegal activities or violates lease terms.Financial Stability: Screening all adult occupants also allows you to assess the household's overall financial situation.

If it was a female dog the puppies would be over the animal limit so that is a no go.