Separate the different uses
List drinking, cooking, handwashing, washing dishes, bathing, cleaning and any growing plans. Next to each, record the proposed source and what you still need to verify. Water suitable for one purpose should not automatically be assumed suitable for another.
Do not judge water by appearance
Rainwater can contain germs and chemicals even when it looks clear. The CDC recommends consulting local health authorities about testing, treatment and suitable uses. If you are considering collection, record the catchment, storage materials and intended uses, then get source-specific guidance before relying on it.
Plan where used water goes
Include the toilet and wastewater arrangements at the start of the project. Their suitability depends on the place and the applicable local requirements. EPA guidance is a useful US introduction to septic systems, but it does not establish what is appropriate or permitted at your particular site.
Write a supply and upkeep checklist
Record how water will reach the place, where it will be stored, who will check it and what happens when the supply is interrupted. Add the local authority and professional questions to your project. Resolve those questions before buying a system around an assumption.