Recognize that in California, single family homes can add one detached ADU and one attached ADU or junior ADU.

Previously I had learned about junior mortgages, but Dean's course focused on first mortgages, which I did not have any experience and are a different animal than seconds or junior liens.

Based on your numbers, do you have a general idea of the total valuation of your entire property prior to and after the junior ADU? 

Generally most mechanic lien and any lien that is junior to the foreclosing entity will be wiped after foreclosure. 

Most people lack the money for a down payment, and their personality tells them if they do have some extra money spend it on a good time, beer, a vacation, new skis, a gift for junior, etc...

Don't play with senior money like a junior.

So the banks who are in second position are cognizant to this and are getting totally screwed when this happens.2. and even more important is the homeowner who lost the home.. if they have no junior liens they are due the overage..

If you've saved enough, trying to house hack a local 2-family in your junior or senior year (maybe with a parent as a cosigner) would be ideal because you can learn landlording and experiment with your friends as tenants.

U can still have a hiccup of course but generally speaking far safer than any junior or unsecured As you have a specific ownership interest that cant be deluded and is first priority in any BK

I just point this out for others.. no one can make guarantees that you will not lose money when in fact the collateral your buying is already damaged and is junior position..