You're better off opting for an interest-only mortgage, saving on payments, and then refinancing it into something more conventional when interest rates drop—or, if possible, making a plan to pay down the principal.Interest-only loans, which typically last for the first 5 to 10 years of the loan term, offer two key benefits.

9) adding multiple ADUs or adding an ADU to a quad looses F/F conventional financing.

Conventional financing will work for this just fine.

Conventional non-owner occupied. 25% down.

I will say that they aren't really yurts, which are a light wooden frame with canvas or the like fabric.

Also, I am guessing that due to the state of the house, it would not qualify for a conventional loan?

Plus you can't typically get conventional financing because they want to finance to a person, not an entity.

Meet with a local banker & schedule a time to talk with a mortgage broker, they'll give you at least a baseline of what kind of down payment options and rates are out there.After that, if you're still wanting to research more creative options, do some looking into seller financing (a very hot topic with good, and bad, advice out there), look into private lenders, and commercial financing options.If you're wanting to live in 1/4 of your quadplex, then conventional residential loans may in fact be your best option as you can purchase that with a fannie/freddy loan with very low down, and use up to 75% of the income from the property toward your own income. 

Is this using a 20% down, conventional or DSCR loan, although I would think a first time investor would use a conventional loan.

I am based in Seattle, but is licensed in Tx.You can acquire your a primary residence from up to 1-4 units for as low as 5% with conventional or 3.5% with FHA with a few exceptions.