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

It needs to appeal to adults and groups as well.

For that reason, never hang up the phone first : )  While it is rare over the decades the number of things we have overheard when they think the phone is off is well, it is actually very entertaining. 

If you would accept them I would vet them like an adult tenant.   

@Steve Armstrong Brandon turner's book on managing rental property has a good section about marketing to certain groups without breaking discrimination laws. to find more college students, using phrases like "close to campus" "short walk to entertainment", "on campus bus route", etc. should help make your listing stick out to college students

I am extremely bias on this subject having been licensed my entire adult life..

I was wondering if anyone here rents to older adults who may need regular services? 

With the level if growth that I am seeing it will for sure become a pretty desirable place especially among younger adults and professionals within the next 5-10 years.

Hagerstown brings a full range of opinions here, which if nothing else, provide entertaining reading as well as interesting opinions.

The main challenge (I believe) with sub-to is finding sellers willing to entertain it.