What do i write/put on mailers

[Gage Green]

My question is what should be written in a mailer? Should it be typed or hand written? What’s the best info to add, should it be on a post card type product or in an envelope like a letter. I’d love to get the bigger pockets community’s opinions. My wife and I drive for dollars, each weekend looking for off market deals. And when we find some I tend to cold call but never get anywhere and I’d like to get something in their hands and in their face as well, as opposed to a missed call or a voicemail. 

Mind you my “we never get anywhere” comment is 2 cold calls and some impatience, but I’m eager and willing to spend a little money getting something directly to them. 

Thank you in advance for any info you provide to us!

This may not be the correct place to post this if not please let me know where you think I may get more feedback.