You will not find a shortage of lots in any of the large metropolitan areas.
A good thing about lots is that they are never homesteaded and typically have little to no titling issues. They can be flipped (if you have contacts) or kept for investment or building.
The best way to pursue lots is to look for subdivisions that are growing in size. If building in taking place in the subdivision then the lot will likely have alot more value. If the subdivision is 'dead' then stay away.
Corpus Christi and Port Aransas are prime for buidling right now. Also Galveston in some areas is also hot. You just have to use your common sense, follow some established techniques and go after it! Its there!