I have started using a spreadsheet but I would like something that makes it easier to keep track of when I have sent the owners a letter or postcard etc; also to attach a picture of the property and some pdf's of county record documents.

Meanwhile, a friend of mine who stated at the same time and is only marginally making it despite long hours is still trying to decide whether or not he wants to spend $250 to send out 500 postcards.  

Quote from @John Laseter: Good morning all, Saturday afternoon a gentleman knocked on my door and produced a postcard that I had sent to his house offering to buy it.

One of the reasons I chose ReSimpli was to also send out postcards.

We found this property through months of door knocking, post cards, anything to make connections in the neighborhood we wanted to live in.

My background is a flipper, so my campaigns are usually simple letters/postcards offering cash and a fast close.

If you send the security deposit disposition to the address they rented from you with ADDRESS SERVICE REQUESTED written in the area between the address block and stamp you'll get a postcard back with the details if the mail is forwarded. 

I'm more wondering what people are paying per piece for post cards vs. envelopes.

If you use a HELOC, I would think about a BRRRR-ish strategy (No perfect BRRRR exists right now unless you go full off-market door knocking/postcard campaign/etc) to where you can refinance and get some of that money back, so you don't have $25k chunks of money at a 9-10% interest rate floating out there indefinitely.

Letters and post cards work well if they are prepared well.