My sourdough starter began with commercial yeast about a year and a half ago. It has picked up native yeast as I have used it, and is no longer the same culture as it was originally. It lives in the refrigerator and I get it out from time to time to make a loaf or two.
Most often, I use the starter as a replacement for commercial yeast and the mixing and rising process is similar. Used this way, the starter turns out bread that is not “sour” but with a different flavor than when using packaged yeast. To get “sour” bread, the process begins with a “sponge” mixture of flour and starter and the rising time is greatly extended.
In a way, bread starter is kind of like cast iron cookware. The best way to keep it in good shape is to use it.
I began with with a culture made from bread flour and then later used a little of that to get a rye starter going.
On the Internet, there are many sites that describe different ways to make your own starter. There are also folks who will share a sample free of charge.
White starter
Rye starter