Rather than buy yeast I decided to be hardcore and capture wild yeast in a jar. It is actually pretty damn easy. I used the method mentioned in the former link, but added a bit of science (or—I've kept a beer yeast starter before). I used my giant bottle of Iodophor to sanitize the jar in which the yeast were to live (starting with a clean slate; I rinsed the jar afterward with tap water and didn't sanitize any utensils), made sure the water used for feeding was at about 90°F, and fed the starter a tablespoon of dry malt extract (maltose being to yeast what fast food is to an American) and a quarter teaspoon of lemon juice (just to slightly acidify the initial mix and make the yeasties new home a bit more hospitable to only them at first) for the first two days. This resulted in a bubbly and happy starter on the third day, made interesting bread on the fourth, and was successfully cloned for someone else on the fifth!
Just remember to measure the volume of the original mixture and write that down so you can easily substitute it into recipes (mine worked out to ⅔ cup of starter from ½ cup of flour and water, but flour varies in absorbency rabble blah moo etc.).