If I am not able to clearly defend myself, to an imaginary IRS auditor, I will pass on those 'expenses'.

In my opion, if you are going to be walking around town or driving for dollars there is no better solution out there then deal machine.If you want to stick to your desk and pull lists to call or mail then I'd say prop stream is probably great.You can also have a local realtor or agent you work with put you on a search for properties that have been on the market over 60 days.Another free option is that your local county auditor will likely have a way to export lists of public data on certain types of properties. 

Further, for people like me who claim Real Estate Professional, this information makes it very plain to any potential auditor that I am engaging in real estate stuff non-stop. 

I would suggest always confirming the TLA square footage on the county auditor's website. 

I have exhaustively read IRC 4975 and related docs (even the IRS guidelines for auditors examining prohibited transaction violations), and I can't find anything to support what I was told by my custodian.

Your best option is an engineering-based study unless you don't mind spending time with auditors. ;-)  Estimates are at no cost and give you the information you need to decide how it can benefit your tax situation.

Every auditor will take any expense from before the placed in service date and will try to REMOVE them from your tax return.

These will be essential in case of an audit or other tax inquiry.Tax professional: Consider consulting with a tax professional who has experience working with rental property owners.

It probably saved me a week of time sitting with the auditor as she went through two tax years in what seemed to be intricate detail to resolve their questions.

They are expecting to also hire auditors, customer service staff, IT, legal support and invest in “investigative technology.