This image comes from the book "The Visual Handbook of Building and Remodeling, Third Edition" by Charlie Wing (available on amazon and other places I'm sure) (The Taunton Press, 2009, Newton CT) It's a great book which I'm sure can answer your question regarding more research. 

We attach a $50 fee for unauthorized occupants and that is a great deterrent.

ciao Hey  April, 1. all of my free professional time is spent researching, working, educating myself on REI. about 20-25 hours. 2. we are using a handwritten style note on white paper with some kind of corporate branding , check out openlettermarketing .com. for visual examples.

If this is a long term hold, which I assume it is, I would not let his concern about real estate values decreasing in the next year or two be a deterrent.

A quick visual of the neighborhood will give you an idea of what to avoid, some are just streets of blighted properties.

As @Ryan Harthan mentioned, a transferable warranty is a plus, not a deterrent, unless you're in an area where it's rare for there to be foundation issues. 

I ran the numbers and made a very easy visual presentation, all of which were options that worked for me.

The thing is, a printer-applied address is a dead give-away that yours is a direct mail piece because the print lays flat on the paper, unlike when you hand-write an address, which gives visual texture.I think too much is made of using yellow legal pad paper. 

If the humidity is as bad as you say it is then the bag will fill really quick and show them, in a visual way they can't ignore, that they're inviting problems by not changing their habits.

If they talk about relocating out of state, help them visualize what that we be like, with your help.