Switching from Computer Science to Historical Linguistics for Master's degree I am a 19 year-old student in my second semester of my junior year of a Computer Science degree. I graduate in May 2020, but I would like to make the switch in postgrad to historical linguistics (not computational).

My long-term goal is to work in academia, hopefully as a professor. I want to eventually get a Ph.D, but I know there are several steps I need to take first.

I have no debt, and I'm willing to take on loans (within reason) to help pay for what's next, and work to pay it off over time. I'm on a scholarship for my tuition, and I work on campus to save extra money. I have a few thousand at hand to tide me over for a bit after I graduate.

I'm bringing all this up because I would like some advice. If I were jumping into computational linguistics, I might be able to apply directly for a postgrad program, but that's not really what I want to do. Would it be more reasonable to seek a second Bachelor's in linguistics, and then look at doctoral programs later? I am willing to do that. However, my school doesn't offer a linguistics degree, so I'd have to go to a different college for it. Do most colleges allow students who've already earned a degree to go back in for another at the same level? I'll only be 20 when I enter again.

Or is there a better path?

Thank you all for reading.
If this is in the US where the undergraduate degree is very generalized then you might be able to go directly to a graduate program in linguistics. You should at least explore that by either visiting a university with the desired program or applying. Of course, your application will need to stress the things that make you suitable for a switch and good reasons to expect success, but everyone needs to do the latter. 

But repeating a US undergraduate degree would also mean repeating a lot of things that you already know because of the long list of requirements. Much of what you already studied in the humanities as part of a CS degree are exactly the same as if you'd studied linguistics from the start. You are missing a few key courses, obviously, but a master's degree, which is more specialized would probably let you fill in any blanks. 

For places with a very different educational structure, like UK with its more specialized undergraduate program, this path might be less feasible, but might be possible even there. But you won't know that until you actually explore it directly. 

However, being successful in any undergraduate degree gives you two vital skills that become more important as you go along. The first is the ability to learn and to demonstrate that you can. The second is the ability to write and to otherwise express your thoughts. Those are both strong indicators of future success in any field.