I've had a few bad apples over the past 8 years, but once you get a system down, its awesome.

You've probably noticed our area has a lot to offer!   

Still have a lot to learn and would like some advice.

hello, aleko. i am a home inspector from the western new york area. the old cloth, 2 wire wiring is kind of dangerous, in my opinion. as stated earlier, the cloth gets brittle and can crumble with the slightest of touch. with rehabbing the place, you are going to disturb it, for sure. then, you have exposed wiring. fire hazzard. not to mention, a lot of this old wiring is made of aluminum, not copper, therefore, the heat it will carry without fail is far lesser that the copper type wiring. if you have an overload somehow, and the breaker doesn't trip, you are going to have a fire. the gfi's have to be grounded, thats the whole idea of a gfi. the g stands for GROUND. with the two wire system you have, where is the ground????

Also the rent was paid in cash and I was only given paper receipts which I didn't retain (or will have to dig to find) Do you think it will beneficial to work out a system with relatives where I pay a portion of the rent and they keep it documented?

Also, for DFW specifically, the North Texas Real Estate Information System (NTREIS) is the MLS for the region and has all the statistics on the local market. 

One of the main reasons I like buy and hold investing is because I can systemize it very easily.

We install flex and ductboard systems, insulated metal sweats worse than these materials. 

Are these just the poor areas of town, or is there a more systemic issue holding the area back from being a good area to invest in?

I have about 12 years experience with a BS in Electrical Engineering and a Masters in Systems Engineering.