There are a large number of recipes available for cleaning products you can make with simple ingredients. Sodium bicarbonate (baking soda), sodium carbonate (caustic soda) and acetic acid (vinegar) are commonly used.
"Natural" really has no meaning in this context, it's not a protected term when used on packaging, so it doesn't necessarily mean anything. You are likely looking for cleaning agents that are non-toxic and don't release volatile organic compounds, in which case the chemicals listed above will provide this. Simply because it is non-toxic doesn't mean you'd be able to produce it outside of a lab, it could be any non-toxic chemical.