With substantial equity in your Fort Worth rental, a cash-out refinance could free up funds to purchase additional properties.

Also, what’s the best way to ensure the area is safe and desirable for tenants?

Also, you will have additional occupancy tax depending whether you are in the city limits or not.

We're fortunate to have an above-average income and live well below our means.This summer, we’ll be moving to Detroit (PCSing in August), and we’ve saved about $120,000 to invest in addition to having funds set aside for the home we’ll purchase in Detroit.The reason I’m posting is that I’m struggling to decide how to best allocate the $120k.

If your focus is on minimizing risk and ensuring consistent cash flow, your current strategy works.

I also want the seller to sign, just to add its own confirmation to the tenant's statements.

Additionally, some states hold Escrow and Title services differently. 

Quote from @Nick Am: @Michael Plaks--> The SE taxes are STRICTLY NOT in addition. 

However, it’s important to ensure the area is safe.

This ensures that any payout for damage or liability can be processed more smoothly, and it can help protect your interests if something happens on the property.