You're never going to get anywhere trying to make a legal argument to a mortgage underwriter, since they typically have zero legal training and will just give something the thumbs down if in doubt.

There appears to be a marijuana grow room built in the garage, it is legal to grow marijuana in accordance with Oregon Laws, however I believe this grow room does not comply with volume of plant growth.

They may be able to refer legal counseling services for this niche.

Syre a homeowner may take out a 200k mortgage, pay the bank for 5 years then default and in the end the bank writes off $450k plus all the legal expenses.  

It has to be designed FOR rental collection. 

If your rental agreement clearly states (and is legal in your jurisdiction to do so) that money received from the tenant will be applied to late fees before it is applied to rent, then you could notify the tenant that you received the money his parents paid on his behalf and you applied it to the late fee and then to rent and that $50 rent is still due.

You have a couple chinks in your armor. 1) she put you on notice that the tree had issues (legally you are responsible for a tree of it's obvious that it's compromised in some way.

That sounds good on the surface but what happens if the tenant legally breaks the lease?

The posts here about these 2 states varies from legal and illegal....Practically all deliverable inventory I currently see is in these 2 states. 

I am not allowed to give legal advice however, until you own it it's not your property.