And the $200K down payment will be part taxable. 

If I'm looking to use private money with person doing it for the first time, is the interest-only payment that I make to my private money lender taxable for them?

So if you sell one of them without doing a 1031 you will have a taxable event.  

Will the 20% (assuming is equal to $100K), be taxable income for the year - even though only equity was received.

Based on the little bit I know, the lenders will need to pay taxes on the interest payments that they receive ("Taxable interest").

The portion of the income that the IRA receives that is attributable to the non-IRA (borrowed) money is viewed as taxable. 

So if your land value is $300k and you're selling 50% of the parcel your DADU lot value is probably $150k or so, and any gains above that would be taxable as capital gains.BP accountants, feel free to shred my reply and provide your professional insight!

ALSO- your a dealer in the eyes of the IRS... so your gains are taxable as ordinary income.

Some of my BRRR properties have had their taxable values re-appraised for as much as a 300% increase in this most recent re-appraisal which is insane! 

Cash-out refi funds are not taxable event.