This is concerning to me but can anyone let me know if I am missing something.

I wouldn’t be too concerned with this.

According to the article, around 5% of the properties are being bought by investment companies, leading to concerns that regular homebuyers are being priced out of the market.1) Do you think this could become a long-term issue, given that the current percentage of investor-bought properties is relatively small?

I'm just suggesting you be well informed:I loved reading Robert Kiyosaki's "Rich Dad Poor Dad"... it was extremely informative and eye opening... albeit told in a bit of a crazy way.  

Counselor called it the most extreme case of rebelling he had ever seen after initially questioning the issue due to our sons accolades/accomplishments. 

I'm also concerned about the liability that I might be exposed to here by allowing what appears to be a business to operate out of my rental.

Those are concerns lenders have.

I see lots of cabins for sale but I’m concerned if the market is strong.

My biggest concern with ADU’s on single family lots is that all the new laws have muddled what the long term value looks like, and most people don’t realize it yet. 

If most of them are available, I would be a little more concerned.