1) medical transcription is usually typing voice recorded dictation into written dictation.
medical coding is reading and transforming the dictation into diagnosis and procedure codes for insurance companies
medical billing is the follow up of claims with insurance companies
2)most people do have to do training for any of the above, in the past you used to be able to just train on the job, but these have become "IT" careers, so there are an over abundance of candidates.
3)some might, usually a smaller company or clinic, but most won't
4) i am not sure about transcription, but with coding/billing, yes and have to have 2-3 years experience.
but i would agree with Mike, make sure you really research this company. there are a lot scams out there.
also, i think medical transcription is kinda a dying career, with voice recognized software, most physicians just dictate themselves without the need of a transcriptionist.
but like i said, there are VERY few people/companies that will train you for 3 weeks, let you work at home and pay you $100-150 a day......just beware