Monthly payments are fixed.  

How will the partnership cash flow cover the HELOC payments if interest rates increase?

Quote from @Brad Roche: The other thing that is great for the FHA 203K loan (not sure about the Homestyle loan) is that you can kick the payments out to 6 months of ownership (so close today and make your first payment July 12th 2025) if you are fixing up the home.

If you do have to move because of a job, you would be safest (in my opinion, i am not giving legal advice or financial advice), i would sell that property to ensure that you did not just purchase with the goal of moving out early and taking advantage of lower rates and lower down payments for purchasing your home as a primary residence. 

In this case, your monthly payment with 20% down will have a good MARKET rate if your DTI works with a much lower month payment and no mortgage insurance(MI).

I have a W-2 Job, capital saved up for a down payment (or two), and a buy box based on my affordability.

NONE of the money raised from the auction of a 2nd goes toward the payment of the 1st (that is why they call it "subject to the first")4.

Unlike the Bay Area, at least from my experience in Sacramento, i don't think the difference in down-payment from a duplex and tri-plex is that significant.

The total cost for this monthly for me is $1.00 fee for online payment for Sevier County, TN and the .73 cent stamp for Blount County, TN.

Perhaps we "buy" the house from them for the $328K balance to satisfy the lender and don't need a large down payment and then have a separate contract with them to pay $x per month until we've paid the full $172K amount.