Typically we account about 10% for architecture and engineering.

Can't write or trust an algorithm to determine home value.

My intuition tells me that the 16 rule will skew AirBnBs pricing algorithm and have some negative effect on search results and display ranking of the largest properties.Huge custom mansions (20 person plus) with a traditionally high minimum nightly rate will now be at a big disadvantage in search results against a true 16 person sleeper (mid size) which has considerably lower minimum rates.The largest properties are now in direct competition with mid size properties as far as sleeping capacity and as a result I expect AirBnBs algorithms will begin to ease prices down on the largest STRs because the mid size STRs will always appear as a much much better value.If my assumptions are correct then what follows is basic economics. 

Hey guys, I'm presently a facilities engineer by trade, looking to get back into the private real estate game.

That type of information would be contained in the plans prepared by a designer, architect or engineer. 

They run an algorithm based on sales.  

@Josue Vargas No worries, Hey that's great I'm actually a working civil engineer as well!

The structure of the home is sound as a structural engineer has shared with us what needs to be replaced and what can be salvaged. 

Cost is everything as an investor, so I'd probably reverse engineer the BRRRR to make sure it cash flows and has equity.

Which is why people probably like ZIllow since I'm sure their algorithm is just raw number-crunching to get an average.