These are just two of the possible methods available, there are a huge amount to choose from and depending on your situation, (whether due to circumstance or practicality) any of them may be more viable than the two I tried.
For more information, check out this video by nurdrage
Copper chloride link( both copper (II) and copper (III) chloride)
All the info related to toxicity of chemicals.
How copper is dissolved in Fe solution
Low power labs
Instructables: using vinegar & salt as an etchant.
10 Etchants for creating your own PCB: Nurdrage