This "addition" is essentially one large room divided in half for two bedrooms attached to the rear of the home.

I've seen many Landlords get their rear handed to them in eviction court because they had non legal leases, etc. 

I just sold a clients triplex who was generating 120k a year gross off the two small rear units.7% on a jumbo loan would be tough.

In addition, two (2) ADU studio units to the rear of the structure under the City of Oakland ADU guidelines, rules, and regulations.

The best view I have of Baltimore is in my rear view mirror 

But, for now, at least there are collections to be seen on credit reports, and there are eviction databases, which just collect the raw data of who filed evictions against who - which is public data.But, really, if someone's credit score is good, with regular on-time payments, and their work history is good, and the length of time they usually live somewhere before moving is good - I just think it's rare to get any real problem tenants if they meet this criteria.Now, they could end up being whiney, picky pains in the rear - wanting new flooring or complaining about whatever, all the time.  

if you just wanted to cover your rear, send a photo of it to your insurance agent and ask him in the email if you need to get any additional coverage for the stairway. 

The due on sale clause (DOSC) is a good concern, but there are ways to legally address is so that is cannot rear its head in the future (my understanding from the team I work with).

We own several s.f. rental properties in NE Portland, including a duplex we built 8 years ago, a major remodel of a 100 year old home next door, and a third one that we will be remodeling this year including adding a rear part-basement ADU.

But we had to tear out all the stairs inside the house and bump out the exterior rear of the house in order to build new stairs completely.