I am using a HELOC on my first duplex to help supplement me on the second property.

(I considered it good practice for screening future tenants.)If you're seeing cheap room rent in places like Oakland, Berkeley, or San Jose, that could be from A) larger houses with lots of rooms, B) older homeowners looking to supplement income, or C) homeowners looking to attract college students or startup employees. 

Any suggestions for good audiobooks to supplement my education?  

Broker-dealers have historically avoided the part of the industry currently being served by the platforms as well because it is extremely hard to make any money there with all of the regulatory burdens absent some sort of RIA co-investment type model that is supplemented by other sources of revenue.  

We are interested in buy and hold properties, SFRs up to four plexes, to supplement our current incomes and create passive income for the future.

I'm an IT professional looking to supplement my income and eventually exit the mandatory workforce.

It is only $395 including the text book and the supplemental study materials are phenomenal, including a math workbook and other online forums and videos for learning. 

If so, you could always help supplement your income by taking on roommates; that's how I started.

Fast forward a some years and now I'm making a good living doing that for a supplement company.

Very good supplemental reading to Hill's book.