Springs are the cheapest good water there is

If a parcel has a genuine perennial spring, that is frequently worth more than everything else on the listing. No drilling cost, no deep well pump, and often gravity fed with no electricity at all.

The federal standard is free and it specifies construction. NRCS Conservation Practice Standard 574, Spring Development, covers collection from seeps and springs including the spring box itself: durable material such as concrete, rock, plastic, galvanised steel or untreated rot-resistant wood, a minimum 1.5 square feet of cross-sectional area, and design against freezing, flooding, livestock, sediment and vehicle traffic.

Call your local NRCS office. They provide technical assistance free, and often cost share. Most homesteaders never call them, and it is the single most underused resource on this page.

Plates from USDA, Water Supply, Plumbing, and Sewage Disposal for Country Homes. A work of the United States government, in the public domain. Hosted here so the link cannot rot. Click any plate to open it full size.

Rainwater

Roughly 0.6 gallons per square foot of roof per inch of rain, before losses. A 1,500 square foot roof in a climate getting 36 inches a year intercepts on the order of 30,000 gallons. Storage, not rainfall, is almost always the binding constraint.

A few states restrict harvesting. Check yours before designing around it.

The best free manual on the subject is the Texas Manual on Rainwater Harvesting: catchment sizing, tank selection, filtration, first flush, and potable treatment. Only its rainfall tables are Texas specific. The engineering is not.

Wells

Drilling is the fallback when there is no spring and not enough roof. Two things to establish before you buy:

• Typical depth and yield in that township. The state geological survey keeps well logs by parcel. Neighbouring logs tell you what you will hit.
• Cost is per foot and unknowable in advance. A dry hole is still billed. This is the largest single uncertainty in raw land budgeting, and the strongest argument for buying a parcel that already has a working well.

Sources