After trying to read that I had to check a mirror to see if perhaps I had a stroke.

Those are the biggest two that are not allowed, but I would suggest checking in whatever state you are co-hosting/managing in.   

We've thought about seller financing, but can't imagine someone selling a $649k house for a small down payment and even smaller monthly checks.

Quote from @Lauren Samford: Check your state laws.

Check out https://www.noradarealestate.com/blog/due-on-sale-clause/in general putting the property into a land trust should not trigger the due-on-sale because of the Garn St Germain Act.

Ignore credit ratings but ask them to explain what you will see during a credit check.

Have you checked Furnished Finder to assess the demand?

I'd check them out.  

I would double check with an attorney if you are going to successfully avoid reassessment.

I highly recommend checking out niche.com when researching the best brrr areas.