There are some additional concerns I would add to this; primarily that such clauses in many states are considered to be what is known as "unconscionable"; so against public policy that they are void on their face.

Public internet forums and blogs are NOT the place to learn real estate, you get ideas, but you're not learning real estate.

Public Toilets are used everyday by a ton of people. 

For example, if I put a property under contract with the homeowner for $40K and then I assign the contract to another investor for $50K, what gets recorded in the public records as the sale price, $40K or $50K?

On the other hand it is a public resource that my taxes have paid for... it's not exactly a commercial image I'd be using.... 

Typically, if you can see the listing on a public facing site like Realtor.com, it's still an active listing however old.Also, most listing agreements include a protection period (typically 1-3 months) after the listing expires that prevent the seller from making a side deal and waiting out the listing agreement.Why do you not want to go through the listing agent?

In it, I take satisfaction in improving the housing for elderly public housing.    

My first direct mail attempt I did it myself by writing the letters and envelopes and then mixed up the to and from addresses (thanks public school system) and sent them all to myself.

In our city, the sign ordinance pertains only to signs placed on public rights-of-way and other people's properties (commercial or residential).  

"May" cover entrance to other units....they are in public view.