I met a guy this month that owns his own energy company who said he can audit your energy bills (he's done it for massive apartment complexes).

I wouldn't recommend putting together one on a spreadsheet yourself as that would be indefensible in an IRS Audit. 

Next year we'll tackle the other half if it becomes vacant. 2-3 years down the road, we will replace the exterior cladding and add another 1" of polyisocyanurate hardboard insulation.Before we started, this building scored a 42 out of 100 - with 12 air changes per hour - in an energy efficiency audit.

You would have to document it, and the IRS would well audit you and examine your documentation.

My accountants will audit all books.

Once you have some basic information and you are able to audit multifamily properties, you'll figure out quickly how the financing will work, what returns to expect and whether you can be in better position (financially) with upgrading to 30+ doors than just keeping your paid off rental portfolio.

@Shaye Mora I personally would not be able to sleep easy knowing they can audit any day, even though there is a percentage chance they won’t.1 year is not a long time counting against the benefits of what an FHA can do to propel you forward.

This is an IRS certified tax expert, who can stand in your stead in the event that you are posted overseas and have to deal with an audit. 

As a pass-through entity, there are no particular tax benefits except that it helps to fend off an IRS audit by showing that you run a legitimate business and all those deductions you claimed were legitimate, but ONLY IF YOU KEEP GOOD BUSINESS RECORDS and do all those things above like write checks and operate like a real business.

 @Ashton Ferrazzo,Yes, using the tax assessment from your county is the safest way to go, unless you think that is not correct and you can allocate more to building, but you should be able defend your allocation if ever audited.