Due to item 1, adding an ADU can require years to start achieving any return (once the accumulated cash flow recovers the initial negative position).4) Adding an ADU is a slow process.

You're giving up some good tax benefits since you're in the tier of taking itemized deductions.

But you do need to give the deal items for worthwhile info.  

I haven't filed a claim all these years but insurance is for the what-if and to be used for the high-ticker items, but chances of damages exceeding the 5% is low.  

One important item to note about bids: most smaller contractors are terrible at estimating.

Once I get to a point that it is making enough per month that I feel comfortable taking money out of the business that would be when I get to the point that it is worth have a specialist assist me in all deductions, credits, and future items that will help me to transfer from a W2 to working for myself fully.

Also, what others have said, the personal touches on what is in your place (e.g. providing all the essentials instead of having people buy TP, coffee, shampoo, etc.) and the quality of those items (no tattered towels, stained sheets, etc.).  

Most new construction deals require you to give up to a 10-year warranty on some items while most fix and flips come with very little extended liability after the sale excluding gross negligence which is not stopped by an LLC in any case.

Are these the only items we need to document?

At the end i will add a list of items why adding a single ADU in single family zoned areas may not be the best RE option.The most common value add is via a rehab.