I include written instructions for payment, reporting maintenance, and how the tenant can communicate with me.

At a bare minimum, I would consider filing a complaint with the state licensing board, but only if you have written evidence (email, text, letter, etc.) showing that you instructed them to install security and they failed to follow your instructions.

Despite paying a substantial fee, I found that beyond basic instructional videos and repetitive weekly calls, there was little substance to aid my learning.

At the end of seven years, the interest and principal is paid back and I have effectively manufactured $60,000+ in cash. 

You can make a digital guidebook to put in written instructions.

I list it in airbnb and Furnished Finders, if they reserve from Airbnb all the instructions are given to them through Airbnb.

I wasn't expecting much from this help button, but it turned out that within a few hours I had detailed responses with step by step instructions telling me exactly how to do what I needed.

There are a ton of free guides and videos with instructions.

What brand/manufacturer do investors typically prefer for new manufactured homes? 

As a Contractor myself, on my New Constructions I use Lawson windows and I NEVER had a problem with these windows that involves quality, I’ve had problems with the other manufacturers that were mentioned above.