Answer

I wouldn’t recommend planning in advance on that kind of employment. Alongside a regular job, you can start developing such a venture and see whether it goes well, and then move over to working in it. It’s a venture whose chances of succeeding and bringing you a steady salary at a reasonable level are not high.
Also, don’t count on a job at a university. It’s very hard to get a position there, especially in those fields. I didn’t understand your question about how much time you need in order to maintain your status. To be at work? That’s not a question of status but of honesty. They pay you to do research, so you need to do research.
I know quite a few people who say that a person should study what he loves and wants, and afterward he’ll already manage with work. Our world today is dynamic, and a person can find all kinds of jobs. History and literature really are fields in which it’s hard to find work with reasonable pay. If you very, very much want specifically those fields, I would still recommend studying them, and afterward you’ll find some kind of job. But if you don’t have a major problem with studying another field, one that brings in more income, then it’s preferable to take a double-major track at university, and after your studies look for work in your own fields, but with backup from the other field you studied.