Since Zillow doesn’t allow live links in messages (even links to articles on their own site), it’s also challenging to direct people to my own website, where integrating a chatbot would be much simpler and more effective.

Agree , those are all incredibly important as is good property management and the ability to price the property correctly based on your competitors rates( dynamic pricing ) . 

This article might help:Blind Mounting

Cash flow is important of course, but so is appreciation, so I want to ensure I have a balance of both.

-Most importantly, this are unsecured investments.

When renting by the room, what amenities are most important?

Verifying last 2 years of rental history very important!

The important part is operating it properly. 

One of many examples of lenders is Fairway https://www.fairway.com/articles/how-to-get-a-loan-for-a-shipping-container-home.

All funds process through various channels but the PMS (with trust accounting which is very important) keep track of all the funds and then we disburse monthly to the owner.