Just google 'rainwater harvesting' and you'll get lots of info, esp from Texas.

Falling on a clean surface, rainwater is twenty time cleaner than the cleanest ground source of water, anywhere.

If you have acid rain, hang a bag of limestone chips in the tank to add a bit of alkalinity.

Plastic tanks are the cheapest, but the most susceptible to UV damage over the years. But if you wrap the tank with a couple layers of chicken wire and apply an inch or so of concrete to it, it will both protect the tank (practically forever) and keep the water cooler. I understand that the moss-like algae growing on the walls of the tank are beneficial to the water.

Two good books on harvesting rainwater:

Water Storage: Tanks, Cisterns, Aquifers and Ponds by Art Ludwig (the Greywater Oasis guy).

Rainwater Harvesting for Drylands and Beyond (3 vols, 2 are out now) by Brad Lancaster.