If the deal is too good to believe it’s probably a scam.
Received from the Westover Hills Neighborhood Watch:
Greetings, a man claiming to be an employee of a security system company may knock on your door. His name is Evan.
He may say that he got authorization/support from Neighborhood Watch to contact neighbors. That is not true. He may also claim that one of your neighbors suggested that he knock on your door.
The deal he is offering (and he may mention Honeywell or Guardian) is to install the system for free in return for a sign posted in your yard. However, it is NOT free and monthly charges will apply.
Here is a helpful link.