Do the math and see if an ADU is worth the cost and effort.https://www.biggerpockets.com/blog/rental-property-cash-flow... 

Quote from @Patrick Roberts: Angel oak and A&D mortgage are two of the bigger lenders that I know of who will do 2nd's on investment properties as of a few months ago.

Plus, you get amazing appreciation potential due to how much population growth, job growth, and companies moving and developing here.

Quote from @Logan Barwick: I Am looking at getting involved in rental properties and debating on which option would be best.

I recommend that you find a trusted or recommended Mortgage Loan Originator (MLO), who can give you options for property-based loans (mostly investment loans) and they don't use your taxes but the P&L of the property.

What type of property? 

@Cole Starin sometimes it makes sense to sell the WORST property in your portfolio.Another option is why do a LOC on the duplex, when you could just do a $100k cashout refi to pay off all your debt AND keep the property?

We are the developer and builder.  

Similarly, if you put several Class D tenants in a Class A 4-plex, what do you think will happen to the property?

Purchase price: $1,485,000 Beautiful estate-like property in the Redwood forest above Santa Cruz CA.