Making sourdough starter takes about 5 days. Each day you “feed” the starter with equal amounts of fresh flour and water. As the wild yeast grows stronger, the starter will become more frothy and sour-smelling. On average, this process takes about 5 days, but it can take longer depending on the conditions in your kitchen. As long as you see bubbles and signs of yeast activity, continue feeding it regularly.
If you're taking a break from baking, but want to keep your starter, you can do two things: