I cannot recommend much about the areas in Dallas, but i can definitely offer my expertise as Mortgage Loan Officer, Investor and Short Term Rental host.Feel free to reach out :)

Saying that, we are only interested in buy-and-hold investments that offer positive cash flow upon purchase and some minor non-structural reno's. 

I received an offer that is substantially higher than my asking price from a retail buyer, but the buyer would have a mortgage and need a warranty deed.My attorney reviewed the title search and the county's notifications to lienholders and doesn't see any issues. 

Is that typical now? 

Realtors typically sell properties ~10% higher on average over FSBO. 

How can I verify the Opex of the property prior to submitting an offer?

Typically, I try to bring my out of state investors deals that meet or beat the 1% rule in rapidly gentrifying areas.

What are the necessary steps, and how long does it typically take?

Typically, the NDA will be integrated into other principal agreements relating to the subject matter of the NDA such as proposals, contracts, representations and agreements.It is always a good idea to separate trade secrets from confidential information in the NDA, this is because trade secrets usually have a longer protection period by law.

Instead of telling me I'm in over my head, why don't you offer some solutions for me rather than offering solid advice of it only takes 10 minutes?