I would start by cold-calling, text blasts, and post-cards. 

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They wanted me to create an online account by putting my username and password on a postcard and sending it back to them.

I would say to send them letters not postcards.

You could connect with a realtor and have them pull a list of duplexes in your preferred neighborhoods in Cape Coral then mail the owners a letter or postcard.

If this is the case, they receive dozens if not hundreds of letters/postcards, over a short period of time.

I put $50 into postcards a month ago and got a $4000 sale few weeks ago.

If you're really struggling finding a good deal, consider directly reaching out to owners via text or postcard.

Otherwise I write handwritten letters (but I'm planning some postcards). 

PropStream does a great job of Skip Tracing and sending PostCards, but it does not provide the ability to send actual marketing letters.Any Suggestions are greatly appreciated!