Years ago I wanted to learn to make good home made pizza. As a result I needed to be able to understand and make bread. I found a sour dough starter at a local privately owned kitchen store. I still have it 4 years later and I keep it in my fridge.
I realized that some day, commercial yeast may not be available and I will have to have a good way to be able to make bread rise. The thing that makes instant yeast great is that it has been genetically selected to rise quickly for making a loaf a bread in a couple of hours. The difference with natural occurring yeast like the San Francisco sour dough yeast (Lactobacillus sanfranciscensis) is that it may take 8-12 hours for a loaf to rise, but the taste is better. It develops more flavor with the long rise time as the bacteria and yeast multiply. It doesn't have to be sour either. If you let a water and yeast mixture sit for a while before mixing the dough, acids will form giving it the sour taste. If you just get your culture active, mix the bread , and let it rise, there will be almost no hint of sourness.
The starter stays in my fridge and I take it out when I remember every month or so to discard half and put more flour and water in it so it doesn't die on me. The bacteria and yeast help each other out. The bacteria imparts flavor and also keeps harmful bacteria from forming. The yeast break down the starches and create gases and sugar for the bacteria to feed on. You can leave it out like they did in the days before refrigeration, but you will have to divide and feed more often as the warmer temperature will cause it to be more active.
It takes practice and I could never begin to teach someone through this blog how to work with it. There are some good resources if you are interested in trying. Two books I have are,
The second being a little more advanced. There are many books on the subject. I couldn't live without bread and you need a good way to use all that wheat you will be storing. In the future I will talk about living food and this is one of the overlooked, living parts of your self sufficient home.
You can buy a STARTER on Amazon if you are ready to try. Later!