I allow fish as long as they are quiet and well behaved.

College students may appreciate a quiet study area or a place to visit with guests while their roommate studies in the apartment.Maybe there's a need for a coffee shop or other small business that needs very little room but also provides a service your tenants would be interested in?

That's an extremely rare opportunity though. 

To put it nicely, I would proceed with extreme extreme caution, if I were in your shoes. 

That is an extremely difficult accomplishment in the near-term.

Note local rules could be more extreme.  

They are two young professionals with money, they have extremely high demands, they "know already" because they talked to their "xyz professional buddies already." 

Im sure you know that philly is very neighborhood specific and markets are extremely hyper local.

AprilApril: Extremely bummed, almost didn't want to get out of bed.

The rep became extremely rude and verbally abusive on a phone call with myself and my agent..