Ok, so I called the repair shop from which I bought the car originally to see if they had any ideas. The guy told me that the bearing should be fine, but that he remembered some underbody rust on this particular car, and that rust might be the culprit. I crawled under the car as far as I could without jackstands, and unfortunately, I think he's right. Here's what I found:
What is this part called, and what does it do? It's located behind the wheel, on the side of the car that's squeaking so badly. As you can see, it's pretty badly rusted.
Just for reference, here's the same part beneath the other wheel well, the one that's not squeaking. It looks pretty rough, too, but at least it's not as bad as the first one:
Again, as dumb as this sounds, I'm not even sure what these parts are called or how they function. Are they difficult to repair? Expensive to replace?
While we're on the issue of rust, I also found this:
It just looks like a strip of metal that runs directly behind and above the bumper. Is it crucial for structural integrity? I sure hope not, because it practically crumbles to the touch.
P.S.
I know I should have checked for these things on the day I bought the car. I was so excited, however, that I just glanced under the wheel wells and called it a day. Guess I learned the hard way on this one.