@Lynnette E.

There are multiple reports on other websites of banks lowering credit limits or closing accounts altogether with no notice at all, just a letter in the mail. 

In December of 2016 I sent out 500 direct mail letters to duplex owners in SE Portland.

I own two 2018 Tax Lien Sale Certificates of Purchase in Arizona, and I read the law governing the 30 day notice before the foreclosure at  https://www.azleg.gov/ars/42/18202.htm , as well as the law governing the foreclosure itself at https://www.azleg.gov/ars/42/18201.htm1) Let's say a property is owned by John and Jane Doe, both living at the property itself, and receiving all their mail at the property itself. 

I have provided transactional funding and acted as a Private Lender many times... 90% of them were organic networking connections, but sometimes, I have gotten direct mail based on the investor reviewing HUD (Closing Statements) to look for Private Lenders and then reaching out...

It does not look like direct mail but it looks like a threat or court order 

Send them a lease offer by US Mail, certified delivery.

Your marketing, whether direct mail or web, has to touch a different nerve.

Does written mean actually mailing a letter to them, or can I just print a letter - sign/date and hand deliver?

I used to work for a guy that would send me out to do estimates all the time and he would never mail or email them out after looking it over.