TexasCHLforum.com

The CAD idea is a good one. To make it easier/less expensive, you should simply request all property data sheets for each government entity in the county, and list them out, i.e. City, county, state of Texas, etc. Also, many have their websites set up to search by owner. You can just type in the name of the county or city (i.e. Travis or Harris) and that will get you most of them. If you get it off the website it won't cost you anything and you won't have to file an open records request. The list of tax exempt properties would include every church, shelter, and charity building in the county, so you probably won't want to be that broad.

As someone who processes Open Records requests for a living, I can tell you that your request is a non-starter. You have the following issues at least:

1. The Tx PIA only applies to DOCUMENTS that are ALREADY in existence. The way your request is worded, you are not asking for documents, just information. Unless the gov. entities you are submitting requests to already have lists of the info you are looking for drawn up, you are going to get a nice letter saying that they have no documents responsive to your request.
2. Even if you reworded your request to ask for the documents that contain the info you are seeking, you are just going to get a wad of unorganized deeds, contracts, reports, etc. Additionally, on a request a broad as yours, you would probably be required to prepay the estimated costs of the gov. entity in preparing and copying the info (10 cents per copy and $15 per man hour spent retrieving, searching, and copying files. The gov. entity can also charge you the actual personnel costs if the person doing the work makes more than $15 an hour) On this type of request, that could easily reach a few thousand dollars for just one medium to large gov. entity.

Honestly, I don't think there is any way you can succeed with this request under the PIA, it's going to be too easy to trip you up on a technicality or justify prohibitive charges. JMHO, FWIW