Ask for a "Pre-Underwrite" this is where the bank underwrites the file and give you a "Loan Commitment" instead of a generic "Pre-approval" letter.

My question is; is it better to not ask the seller to pay for the buyer agent's commission (not include it in the offer letter) so that I pay it by myself and get a tax write off on this commission expense for the ADU's sqft portion?

@Katharina Bormann in my experience they don't like those official looking letters in the mail so make sure you do that and also have a cost associated with unresolved issues like trash in your lease. 

@Jae Yoo you have a few options:1) Hire an attorney to write a threatening letter.

I will drive the neighborhoods I like at least once a week and jot down addresses of houses I believe would make a good value add and write a letter to the owners. 4 - I will speak open and honestly to my group of fellow like minded investors to pass on anything I have learned and help those who need a hand getting started.5 - I will achieve my first partner or group partner deal 

As an investor, you'll need to wait until this period expires before your offer will be considered.Additionally, Freddie Mac may require proof of funds or a pre-approval letter with your offer, and they often prefer cash offers or conventional financing.

HCD has no bite, but they would send a cease and desist letter to any entity that is trying to remove a safe unpemitted unit as their mandate is the protection of the various housing mandates from over zealous local jurisdictions.  

letters.

We use carbon copy in letter size (legal size is just a pain).

Is he going to just tell you to knock on doors and write letters, or is he going to introduce you to well vetted agents in your market that are known to source deals and sell for realistic prices?