Then I had to open an LLC for some other investments.

I’ve got a TN LLC that I registered as a Series LLC (with series language in the Op Agreement).

Outside of having the LLC you'll need separate book & bank account for the LLC to operate it separately.

If we want to do cash out refinancing, custodian of the SDIRA LLc will have to make the call? 

This is my personal opinion, which probably won't be popular.If you are worried about the cost of hiring an attorney to create a proper operating agreement for your LLC, you probably don't need an LLC, and if you choose to use an online site to create an LLC, you probably get the protection you paid for.

Quote from @Brittany Kelly: Quickest way to put single family home rental into LLC.

@Phil Petite Forming an LLC in Tennessee is recommended if your rental properties are located there, as it simplifies legal compliance, avoids the need to register as a foreign LLC, and aligns the LLC with Tennessee's laws for property management and tenant disputes.

but keep in mind CA has higher taxes and reg fees and I’m not doing more than 1-2 flips (short timeframe flips)  a year and many years do 0 flipsDo most flippers put flips into LLC Or in personal name (sole proprietor)  in CA (where you must pay $800 yearly plus accounting and other fees $300to $600+ yearly to maintain LLC) Pros for personal name-save on taxes accounting.

You will be personally sued along with your LLC.  

I'm the member and manager of Skeeters Residential Renovation Services LLC