I am an accountant but dont specialize in that kind of transaction accounting and wouldnt do my own bookkeeping or even do my own taxes if I had any of these complex situations to be honest since I dont do that everyday and the tax law is so intricate and ever-changing.

Your basis is still only $100K as would your son's basis if you gift it while living. 

One of my family members is buying the house, 2 other family members are gifting 66% of the funds, from there after it closes we’re going to transfer the deed to the LLC where there will be 3 partners, in which we’ll need a partnership agreement setup.

Send them a small gift card for their birthday and Christmas to show your appreciation.

Sounds more like a gift with the LLC as a nominee

Most DSCR lenders will accept unlimited gift funds so if you have someone who can gift you the money to get the loan amount down, it could work. 

@Jordan Lagrassa      Jordan,          Your father in law can simply gift the property to you at any time or add your name to the title without even having to notify the Bank (Intra-family transfer).

As Gary Keller said, "Listings are the gift from the Real Estate Gods."

It is around 40k so can i gift that much to him?

I just don't see busting my rear for a few bucks and besides that rentals are the gift that give over and over.