There are a couple things here that should be understood: - The definition of a "valid" contract is one that is legally binding because it conforms to all legal requirements for the contract

I can think of some laws in several industries that I do not like, or agree with, but I respect them & conform to them because I dislike the penalty fees even more.

The Survey is focused on conventional, conforming, fully-amortizing home purchase loans for borrowers who put 20 percent down and have good credit.Los Angeles Airports Stalled.

. - "Conforming high balance," not conforming.

But it is not a conforming non-portfolio product.  

@Stephen Roy The fact that it is listed as a 4 plex but there are actually 5 units probably means that one of the units is non-conforming, so you definitely want to bring this issue up with the seller, and find out how to make it a conforming unit (a value add), and why they haven't done this before.

It's more like "Work conforming to MY specifications".

From what I've found, the subdivision I'm looking at is zoned / cleared for ADUs as long as the build conforms to the guidelines.  

Laws and standards vary from state to state and each unit would need to be legal and conforming to zoning (say zoning codes require 0.18 acres per house and this would leave one parcel at 0.15 acres... you couldn't do it).

I say this because in Hawaii you cannot have a Short-term VR without a non-conforming use certificate, which hasn't been issued since the late 80's (bogus politics in part of the big hotel lobbyists).