So many new improvements from up and coming districts toshopping and attractions in parts of the city that used to be completelyrun down.

As @Ross Denman has pointed out, if you are truly in the historic district, you will have a lot of restrictions on what you can and can't do and need to get permitting. 

Even has a very high ranked school district thats major struggles are due to the population and enrollment.

@Stephanie Potter I have two properties that came my way, both in great school districts.

Usually means good school district, low crime.

We were told it has the best school district in the market and there was very little rental competition there.

Does anyone that has experience renovating historic homes located in historic districts that can give me a rough idea on the additional costs associated with them?

Taking advice from people that live in a different district is useless at best, dangerous at worst. 

Did you get lucky you found one in the district you or your spouse lives in or am I missing something.

I normally estimate property taxes at 1.7%, in most of DFW that is about right.Insurance is also extremely high in all of Texas (thanks to the people in Austin).The best market to invest in is the one you know better,,the difference in two houses, one block apart in the same city and school district can be more than you think, one might be in a 'in demand' high school area, the other one may have students going to a less desirable high school,,,as far as rentals go, the difference in rent rates and how long it takes to fill a vacancy can be affected more than you think by things like that