@Kevin Leppink first thing first is that I have never done a direct mail campaign but I have been getting some ducks in a row as I have been deeply considering starting one with the simple goal of picking up one rental every 12-24 months or even finding a property to house hack. Here's what I've found out from the research I've done and the people I've talked to. Again, I have not done a mailing campaign and I'm no expert. These are just some of the steps that I've taken in order to prepare for if I do end up marketing for rentals for me.
-Find somewhere to get your list i.e. ListSource. The list will include the mailing address of the owner I believe.
-Find someone to print your postcards, letters, whatever. Supposedly it's best to send a postcard first because it's the cheapest and you'll get the non deliverables back returned to you so that you can further scrub your list or skip trace those returned cards and find the real addresses of the owners. Make sure you use a first class stamp for this reason. There's lots of shops that will print and mail for you. Yellowletter.com is just one off the top of my head. Do a search on BP and you'll find a ton of info.
-Make sure you have enough money for a sustained campaign of 6-8 mailings.
-Make sure you have some kind of phone number local to area. There's lots of different apps out there but the one I was going to use was just Google voice.
-Make sure you know all the questions you need to ask the potential seller to determine why they want to sell and to see what are any issues they have and how you can solve them
-You'll need someone to help you with rehab estimates if you don't know how to do it and you'll need someone who has access to the MLS so that you can figure out an accurate ARV.
-You'll need a title office or real estate attorney. Here in UT the two that I know of are Jax Pettey at First Liberty Title and Jeff Breglio. I've talked to Jax and taken a seller finance class from him that was really good. I haven't had any interaction with @Jeffrey S. Breglio but he's on BiggerPockets I'm pretty sure and I've heard that he is a good guy for what that's worth.
-You'll need contracts for the seller to sign so that you can put the property under contract to buy. The type of contract will depend on what you are doing with the property i.e. buying for yourself, flipping, wholesaling, wholetailing etc
-You may need a CRM to keep track of leads etc but that's really probably more for when you scale and start doing some volume.
Anyway, I hope all that helps. Oh, since you are local to the Salt Lake area make sure you connect with @Jeff Rappaport, who hosts a wholesaler meetup every month that is really awesome. I've been to a few of them and they are a wealth of free information and networking. I haven't been able to go in the past year or so because I travel for work and my schedule can get crazy. Jeff also does a relatively new podcast called "the creative financing podcast". I haven't listened to many episodes but it looks like they interview a lot of local to UT experts so that's awesome for us UT people. @Jeff Rappaport