medwave

There's a lot that goes into it and it's heavily dependent on practice(s), but you can either take classes (get a degree) or learn it on your own, as I did. I stumbled into medical billing and credentialing while working for my mother's PT practice and it just grew organically and exponentially with some fairly large behavioral health contracts. TBH, I just never looked back and taught myself everything. Meaning, you can do it, if I can do it! :-)

I don't think you need your own medical billing software per se. I would find out if the client you have, that is outsourcing the job to you, has their own software that you can and should use.