I started a batch of buttermilk today. Now this is easy. In a quart canning jar, add 1/2 cup of cultured buttermilk to 3 1/2 cups of milk, whole milk is preferable. Allow to sit on the counter for 24 hours and it's done.
To make sour cream use heavy cream in place of milk.
Save a little from each batch to start another fresh batch, as in making sourdough.
Easy enough eh?