Option 3- If they have qualified for FHA; counter the offer to see if they can qualify for low downpayment conventional loan

Nothing builds credibility more than telling your lender that they are protected with loan documents you got from a stranger off a website.  

I would look at the DSCR loan as the first option.By the way, I suspect you are going to be disappointed by any refi appraisals   ADUs typically appraise poorly   JADUs can lower the property value Vs having the space as part of the primary unit.  

DIRECT MORTGAGE LOAN COMPANY6.

Yes I know about the VA loan (no down payment) and VA disability payments, more on that later.  

25 inspection, 25 closing, 1 loan.

The most successful loans are those that do not procrastinate and get the appraisers In ASAP so you can get over any unexpected bump in the underwriting process.

Loan Amount: We specify this as a percent of the purchase price.

LTV would be determined by the type of loan.

OO loan seems like real long shot.