The biggest danger is a leaking tank that causes water damage, but it hasn't happened to me yet.

If $23k is just a “hope and a prayer” then he’s going to have a very hard time producing any CREDIBLE itemized bill.  

Carrybacks are super dangerous.. but...

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.

For instance, not knowing what type of panels are on the naughty list in the eyes of the lender will trip you up during a DD period if you haven't underwritten your line item expense of replacing them.

If you use Hospitable for comm mgmt, Turbotenant for all tenant mgmt related items, and FFinder/your own website/Turbotenant for lead acquisition -- how do you describe your work flow across these?

The address was submitted to their red book and now shows up online as official address when I try to ship items from Amazon or similar websites.

Develop an itemized list of the various risks specific to your proposed investment, and the cost to you of each.4.

@Jesse Jones-Smithhi. i tend not to advise people on personal residence items because... it's too personal. so i'll just pick one thing you mentioned and provide a comment. 

I'll preface by saying I'm not a tax expert, but just went through a cost segregation as a REPS and this was my view.The benefit from pulling out these items coupled with the bonus depreciation far outweighs any incrementally higher taxes in later years, by quite a large margin.