Setting up a home creamery to make your own dairy foods is really very simple and one of the best things you can do to economize. You'll also end up with better dairy foods as a result.
Mark Bittman's How to Cook Everything has a simple recipe with no heating requirements. First, sterilize a jar, then heat it carefully with boiling water until it is quite hot. Pour in a cup of heavy cream at room temperature, add 2 tablespoons of cultured buttermilk, then stir to mix. Close the jar and wrap it in a towel to keep it warm and cozy while it sits out overnight.
In the morning, after it had been sitting about 12 hours, I opened the jar to stir, and immediately noticed how much thicker it was than my previous batches. The flavor was nice, but still more creamy than sour, so I closed the jar and rewrapped it to sit out all day. After it had been out about 24 hours, I put it in the refrigerator to chill overnight.
This method produced a tasty crème fraîche with enough body to satisfy me. Next time I'll let it sit out for 36 hours to develop a slightly more sour, nutty flavor. If you want to make crème fraîche without using a culture, this is the method and recipe I recommend. It will keep 1-2 weeks, but I doubt it'll last that long, because it's really delicious!
Setting Up Your Home Creamery
A simple home creamery requires a few pieces of kitchen equipment. If you don't already have a good, accurate thermometer, get a high quality instant-read thermometer. A good stainless steel 2-quart covered saucepan will be your basic pan; a larger pan is usable but can be difficult to control unless you're doing larger batches. For measuring, you'll want a 4-cup measuring cup and a good set of measuring spoons. You'll also want some unbleached cheesecloth on hand, as well as an assortment of jars--I prefer french canning jars and bottles with bail tops.