Other things such as adding bedrooms, bathrooms, square footage justifying permits.

In southern CA, even garage conversion ADU additions are typically costing more than the value added.  

The second best time to plant a tree is certainly today.

Note that Sec8 comes with added costs & issues due to bureaucracy and state of the HUD departments in the area.

Plus you can plant on top of it.

Pretty solid appreciation in that area with an average of 5-7% per year, and it's also close to a lot of industries like the Chrysler plant.

Although this is a long term investment and not in the main stream, it has added a certain level of comfort knowing the above potential investment risks are to a degree reduced.

Nate @Nate Marroquin   You can use the income from your tax returns on the current rental adding back your paper loss (depreciation) and add back the mortgage interest, property taxes, home owners insurance deductions on your tax returns. 

Here is a list of why adding ADUs in my CA market is typically a poor RE investment:1) The value added by the ADU addition is often significantly less than the cost of adding the ADU.

Use an attorney for added pressure.