Ammonium Persulphate or Ferric Chloride are the most commonly used etchants for copper PCB's. They also work well on brass, and are not nearly as hazardous as acids. Dry film photo resist can be found on EBAY along with developer. Glass baking dishes make good etching and developing trays. Photo resist is UV sensitive and can be exposed using a tanning lamp, or bright direct sunlight, or you can purchase a dedicated UV lamp. Plan on wasting some of your early attempts as you learn the process. Brass shim stock is a relatively inexpensive material to experiment with. It is possible to etch from one side only (the back fully covered with resist), but it will take longer and there will be more undercutting of the edges. If you are going to etch from both sides registration is critical, as even a few thousandths off will destroy a fine part.