I forget if it was explained or not why Darlene moved into an apartment instead of a dorm. I guess it's easy enough to deduce that there were no dorms at her college, or at least not for a girl who wasn't even eighteen yet. But how did she end up swinging her parents renting her her very own apartment, with no roommates or anything? That must have been a pretty big expense to add on to the Conner's already hefty monthly bills...

I don't ever remember any mention of the Connors having to pay for her apartment. I have never come up with an explanation either.

Well that apartment couldn't have cost too much..it was nasty.

In the episode Tooth or Consequences Darlene says that she has a scholarship and she can work at the bookstore to pay for her rent. She also asks for money from Dan and Roseanne in a couple of episodes in season 7

Yeah, and some colleges offer student housing on campus. The apartment might still have been on campus, I had friends who did the same.