FYI these aren't quick questions that we can give you quick answers to. It takes time to learn -how to craft your approach(es), and it takes time to learn enough about an industry (for example healthcase) and sound credible and bring actual value to the work.

All that said, jobs vary. If you are contracted by an agency, or by a client that has in house marketing/researchers , you will get a creative brief at the start of the project. This is a short document with info on target audience, objectives, and sometimes brand voice. Often you will be provided with statistics, facts, or studies they want you to include. Other times, especially if you are working for small businesses, you will get much less information. And some of the research, etc will be up to you. Sometime you may be asked to establish brand voice. It's best if you at first seek jobs in which teh brand's voice is well established and learn to match that voice, rather than reinventig the wheel every time when you are new.

I want to go back to something I said above: value. Often here when people are new and looking for clients, I see them ask about expecattions, tricks, everything except value. If you start from zero and are self taught, get honest with yourself about the value you can offer. Especially if you want to work in the healthcare field. If you cannot yet bring skills and knowledge to the table, that's okay. Look for projects with extremely clear expectations and a well-established tone. And/or projects or jobs where you will get to interact and work with copywriters with more experience.

Avoid the spiral I see with self-taught beginners who look for jobs on upwork etc. I see self-taught people enter the field with bad, low-paying clients. Then they write low quality copy, the client does not get good results, and they use the bad samples for their portfolio.