You can get used ones ones on craigslist. For covers, I think motherease airflow covers are the most waterproof. They are about $10 each at the Motherease website.
As for washing, I use the cheapest fragrance-free stuff I can find at the groceiry. I usually cold rinse, hot wash, hot/cold rinse with baking soda. It works pretty well. I do have to throw a little bleach in every now and then as the diapers begin to retain odor from solid waste and then every time my little guy wets, it smells like poo. Bleach isn't very good for cloth diapers, but I haven't found anything else that works.
Best of luck!