Block construction cement floors with the floors sloping to a central drain. concrete counter tops stainless kitchen cabinets boob lights and minimum windows by code .

Some investors know block by block which places not to invest in.

That's not to say you can't do well there, but I'd encourage you to look at Belton and Temple (which can also be very rough and block to block) rather than Killeen.The good news is that there continues to be serious population and job growth in the area.  

I've lived and invested in areas like this before, and I know it can vary block by block.

A suggestion about Furnished Finders, their calendar sucks because you can't block off your high-season months, a real detriment to taking bookings through them.

The smart play would be to build a two story wood frame structure on top of piers or concrete block in most cases. 35 feet is a pretty typical height limit in most neighborhoods, so depending on elevation you SHOULD be able to build two stories on top of the elevated foundation.

We found out the potentially the whole block has led pipes so we are needing a contractor to cut a hole in the floor.   

As part of the project, the only existing drain on my side of the street is being sealed over with concrete and even that will be lost.

We just discovered a crack in the concrete slab foundation that is a borderline major problem:- It is a vertical crack about 1/8 inch wide that is at least 9ft long, which is causing a 3/4 inch drop in the flooring and some evidence of old (luckily) limited moisture and termite intrusion. - BUT, it also appears old and probably a symptom of the original house settling.

As a wholesaler, a seller approached me with a 48 unit apartment complex, 7 duplexes and a 2500 sqft Single family that he wants to sell (all of which occupy the same block.)