If you buy a package of 6 lesser houses  that means I have 6 roofs, 6 hvac, less cashflow, and likely subpar appreciation(dollar for dollar) compared to better areas.The reduced maintenance costs, higher rents, better tenants, appreciation, and reduced hassle factor for new construction are real and attractive.  

I'm not as familiar with Ft Worth but here in BCS my fourplexes only cost about $50-75 per month for water.

What I would be concerned with is if you can lower your cost of living.

The buyer can add a performance deed to the transaction which basically states that if the buyer defaults on the loan, the property is transferred back to the seller without a long and costly foreclosure process. 

The wear and tear on hardwood floor - carpets has no recourse beyond the deposit damage if there is pee or replacement costs needed.

A roof on a typical duplex may cost $8k to tear off and replace.  

question can I roll renovation cost into the DSCR loan?

In your case, this appears to be $800k - $600k = $200k.You made no mention of the rehab costs.

So they'd loan about 450k if your ARV is 1M (assuming this ARV is accurate), and then you can get a gap lender for the difference (180k plus closing costs/points/etc, holding costs).  

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