I own the property in my name so in my county I can represent myself but for the cost, it is worth it to have a professional that knows what they're doing handle it, and also having someone to answer all of your questions is nice.3.)

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'd be glad to have you as a power partner.

question can I roll renovation cost into the DSCR loan?

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

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

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

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

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

Buyers have significantly more negotiating power.