SMLLC is disregarded and does not have a separate filing requirement (gets reported straight on the Form 1040).I can't speak to the implications of a potential divorce, I would consult an attorney. 

We did set up a separate LLC and purchased and manage our properties finances through it.  

I further believe (though would not underwrite to this) that this approach would offer the buyer the potential opportunity at a future date to conceivably subdivide the parcel and sell the main unit and ADU as separate properties.

I am thinking that perhaps we could insure building and operations separately and that might open some options in insurance providers.

Propstream is integrated but that is a separate subscription.

I am now looking for advice on how to structure my bank accounts to properly separate my personal expenses from any expenses surrounding my house hack.

Keep the agents list and the investor lists separate and you should have another good out for your deals.I've also worked with builders in the past, sometimes some of the smaller builders will flip houses as well if they can slot and ADU somewhere on the lot.Best of luck!

The cost of housing has definitely began separating classes in this country and generations.

If so, to be specific, do you create separate WIP asset accounts for each COGS account, or can you just accumulate all your COGS for a property and put it in one WIP sub account under the Main property asset account?

There is not a separate entrance to the basement, but the stairs to the basement are in a laundry room in the back part of the house.