I gifted my children several homes and don't have a clue about how the IRS documents work, but somehow the IRS allows people to gift real estate for of something like $10 million+ in their lifetime and the person receiving the real real estate does not pay taxes unless they sell it.

I have found this to be beneficial as a poorly operated multifamily generates less income translating to lower property valuation. 

If a LLC is formed by multiple owners, does hard money lenders or lenders accept, one or more partners signing the documents on behalf of the LLC or should all partners sign the loan documents ?

Add any new tenant to the lease 100% so that there is a legal document if/when issues arise.

Several other documents on the registry of deeds as well. 

I agree that it may not be beneficial for taxes, but where it does benefit is that you can start building a credit line with your entity’s name.

Hi all, If I'm considering purchasing a duplex where one unit is a Section 8, is there any additional documentation/paperwork beyond the lease that I should ask to review when conducting my due diligence/property analysis?

this is why CA went to police style thumb prints on Notarized documents that transfer title. 

.- Partner is acting as the bank and I'm going to pay them "mortgage" payments plus interestWhat documents do we need to write up?

But that being said, there are many accountants out there who will let you do it as long as it is very tightly documented as an arms length business like transaction.