Nearly all of the sub-cities around Austin and Dallas, and Austin and Dallas themselves, for instance, have minimum interior area requirements spanning from 1200 to 2000 square feet. Red Oak, just south of Dallas, is particularly egregious.

The smallest house you can build anywhere in the city of Red Oak is 1650 square feet (and there are only a couple of small pockets where even that is OK). The other zoning areas mandate 1800 and 2000 square feet. It's a nice area, with some nice property for sale, but the rules are absurd.

Here's the zoning categories in Red Oak (left menu allows choosing the various zoning categories; notice that even agricultural land requires a 2000 sq ft house, and prohibits all "temporary" structures, like mobile and manufactured homes):

http://www.redoaktx.org/380/Generally

There's also a huge amount of (cheap) land in Bastrop and Lago Vista, to the east and west of Austin, respectively. Same basic story; mandates a very large traditional house, no mobile homes, no manufactured homes (ruling out a "tiny house on wheels", which is how some folks get around zoning or at least evade code enforcement for a while). Even worse, natural building techniques are ruled out by the aesthetic requirements; they'll often mandate brick/stone/stucco, etc. front.

Houston seems like it should be a breath of fresh air, as the city itself has no zoning laws. But, there are often deed restrictions that convey with the property. And, because the deed restrictions are effectively private zoning laws, enforced by the city, they can be harder to track down if the seller doesn't tell you about them in their ad. In some ways, Houston is nicer; deed restrictions often date back before the McMansion phenomenon, and so they very rarely mandate large houses (though I've seen 800 sq ft minimums, quite a bit, which is still pretty big), but may impose other restrictions that are onerous. On the plus side, the enforcement in Houston is reportedly complaint driven, so I think one could probably get away with building small in Houston, as long as you're up to safety codes and on good terms with your neighbors. But, more research would be needed; I've mostly settled on either being near Dallas or Austin if I end up buying in Texas, as I have more friends in both of those cities than Houston.

What's interesting about a lot of places with these rules in Texas is that people seem to buy the land and stick mobile homes on them anyway. I guess they do it without getting a permit (the land I'm looking at is somewhat isolated, so I can see how one might get away with that for a while). Browsing Google maps reveals tons of examples of mobile homes in neighborhoods that clearly aren't zoned for them.

The Bastrop example is one that is especially annoying, for me. I'd love to be near Austin, and there's an entire massive subdivision of hundreds of vacant lots called Tahitian Villages. The land is cheap and plentiful but includes onerous building rules. I'm frustrated that developers seem to come into cities, acquire huge swaths of land, get special treatment by the city to impose additional usage rules, and then they end up going bankrupt or abandoning the development (presumably after cheating people who bought property in the neighborhood at retail prices based on promises of a completed development), leaving a bunch of prime land that can't be used in any way except for McMansions. Lago Vista seems to have an almost identical story. It's frustrating that there's so much vacant land, in a region where housing prices have doubled in the past few years.