There’s a good video at: Cultivate Your Own Wild Yeast Starter Which explains how to get started making your own yeast. The video is just for making starter so you don’t need store-bought yeast. The bread you make depends on the flour and other ingredients which you choose for the bread — wheat, rye, whatever.

This won’t necessarily make bread with that San Francisco Sourdough flavor. If you want sourdough starter, he mentions how to get that flavor in the video. If you do want Sourdough bread, check out How To Make Sourdough Bread Masterclass

Then if you have starter you need to feed, take the part you’d throw away and dry it. Seach YouTube for drying sourdough — drying sourdough starter Then you’ll never run out.