If your phone is not ringing you probably need to make a marketing change.  

I'd rather miss out on that $100 and not have to deal with the FBI over an alleged drug ring scandal, nor (which would likely be more common), haggle with the tenant over $5 that exceeded his $200 utility spending limit.You could say "$5 isn't worth arguing over", but understand that once you set expectations, you need to enforce them consistently or people in general will take advantage.It's really up to you though.

One my goals in the next 6 months is to expand my knowledge past the midtown/1st ring suburbs area, and see if there are better numbers elsewhere. 

You have to send out hundreds of letters/postcards on a consistent basis to get your phones ringing.

Our local police recommend ringing the door bell three times and knocking three times, to try to draw out a response prior to entry. 

You never have to flip through a key ring trying a dozen keys.

@Taylor Comer I second the advice about Google voice - free and super useful - you can forward it to your cell, have it be just on answering machine, customize greetings, etc. when the number gets called both my phone and my wife's phone ring and when a message is left I get a text and an email transcript.

It's really there for the peace of mind, I can always get in regardless of what car I am driving (rental key ring is in my car) or if police or fire or medical personnel needed to gain access, they can always get in--without bulldozing the door.     

Also as I scale I don't want my phone ringing off the hook that something doesn't work, or whatever the need may be.  

Was inside a "for rent" house after a showing when my phone rings.