Remember that in most places, the permit recipient is responsible for passing inspections with code enforcement.

The yellow letter can freak out the recipient.

Is this a worthwhile endeavor given that the number of recipients is presumably much smaller.

You may be "setting switches" in the reader's mind you don't necessarily want to.Try something more focused on the solution to a potential problem for the recipient:"I'm looking to buy a home in your house's neighborhood.

In May of 1970 the US Supreme Court ruled a person can require the USPS to issue an injunction against a mailer prohibiting future mailings if the recipient deemed the mail 'offensive' in any way.

Bottom line:  any paper will work, as long as it looks hand-written--either cursive or print.The envelope is far more important because that's the first step in getting the recipient to open your mailed piece. 

Respectfully,[Your Name}[Business Name][Telephone Number]You will mail this letter immediately upon the completion of your list, and include business cards with the recipient’s name on the back.

My understanding is that the recipient of a gift is not responsible for the tax, the giver of the gift is. 

I completely agree with Dev Horn...that you need to make sure you TOUCH each list recipient a few times over the course of several months.

My mailers are designed to provide a lasting impression to the recipient, one that gets them to remember my clients over their competition, which is an invaluable trait.