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.

I knew I could easily find tenants/roommates as the area is popular for young adults.

I am looking for a rental property as well, for a residential assisted living or Adult Day Care.

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.

She has only said we need to talk like adults, which I have sent several olive branches.

This is time for adult lessons, which includes meeting your financial obligations.

However, as a young adult it is great life experience, so if he can go for cheap, why not? 

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.