I see these week-long boot camps to prepare a person to take the exams like CPC but I can't afford it right now. I want to start working as a coder, can I study myself and go take the exam or do I have to obtain some kind of training certificate?

I see they have self directed study modules on the aapc site but these are expensive, too. It looks like I could get the materials I would need to learn coding on ebay and I see they sell a study guide for the exam, too.

You can train yourself to be a coder. I would recommend that you pursue a coding credential in addition. Many nurses go for the CPC because physician/outpatient based coding is not considered to be as intense as inpatient coding. You will still need to be willing to spend some money on training resources, however. For ICD-9-CM, Faye Brown has a great workbook in my opinion. It's strong on the ICD-9 coding guidelines. If you're going for an aapc certification, I recommend using their workbooks. I would recommend intense daily study for a minimum of three to six months (most certificate programs last nine to twelve months). I also would recommend if you can afford it to join the aapc and attend their chapter meetings in your area. Networking can be very helpful in breaking into the field and getting a position especially since experience is normally required for the majority of the coding jobs.