I have searched far and wide turned up little on the matter of common expense allocation.

Below is a brief description of my holdings:-Two LTR properties that used to be primary residences and are not associated to any type of business structure-One primary residence that will become a rental in the next 12-24 months-Two LLC's that do less than $10k revenue per year-My wife is a Realtor and will soon be licensed for state-sponsored childcare-I have a W2 full time job-Will be creating an LLC to trade stocks, options, and futuresI live in Arizona, using Turbotax Home and Business, and I am ready to pay for something better-suited to the expanding array of things going on.

Pittsburgh has a pretty wide range of property values, but still affordable. 

use caution do not send any money up front no other company will ask for money up front other than appraisal but again even if they dont nick you for deposit money you dont want to lose the deal and or your EM when the lender cant fund.. there are NO nation wide Hard money lenders that do not have NMLS registration and state license.

But Fannie Mae's decision makes it a more widely-accepted practice.  

Wide enough sewer pipes to prevent blockage?

This is very important:  If you have a claim arise, a standard homeowners policy will likely not cover the claim.CBIZ is nation wide and should be able to get you a competitive quote.

Structural engineers have a wide range of expertise in different material types that would require me to entirely pivot my career field.Currently my thought is to limit my service to providing stamped drawings for permitting of minor alterations of existing wood frame structure such as windows, doors, and load bearing walls.

We have an investment property under a LLC (originally owned by my wide and I), recently we added our two sons' name to the LLC.In the future Can we sell the property and distribute the proceed to all members?

I've done single family, flip, rentals, built some from the ground up, rent to own, mobile homes, a small subdivision and I eventually graduated to an array of commercial real estate investments.