It would also be good to do a google search to see who else is out there and what is not out there. 

If you are supplying the funds, then I would probably try to get added on as a lien holder on the property.

.$310K for a 7 unit (depending on unit size), sounds like a deal even in a D neighborhood/D property IF and ONLY IF, you paid cash or already had terminal financing.

The dilemma is whether I should hold more of them instead for the added benefits of: appreciation, tax benefits, and amortization since I don’t need the flip income to cover my personal and business expenses and I’d have none of my own dollars invested.

I'm asking because from a few hours of googling around, it seems like the numbers across website are wildly different (I've seen from ~5% to 10% for the same exact zipcode), and I'm wondering which ones the veterans trust?

Going forward it is not that different because you would be increasing it from 27.5 years to 30 years under ADS.

To get an initial feel for a market I recommend looking at:Population growthAverage Income growthProperty value growthRatio of property owners to rentersDemographicsLarge economic drivers (Hospitals, Army bases, Universities, other large employers)Street view on Google mapsYou can find all of this information with a Google search. 

I have an impression that labor in fortworth is not that expensive and general pricing over the google search came out way below the pricing my property manager charged me. e.g.

I plan on telling him I am ok with the switch, provided the new tenant is added to the lease, the new tenant passes all the usual screens.

Google it in your area.They also have a monthly Deal Maker Session meeting where about 75 investors get together to buy and sell exclusive (non-MLS) properties every month.