rhetormethis

This is entirely right. Actually reporting the income can get complicated if you don't have a W-2 or 10-99, but yes you are supposed to pay for it. UC Irvine's website explains it in a way that's much more helpful than most university's grad departments' stock answer of "we can't tell you anything, go talk to a tax professional."

You also need to take things like moving expenses into account when figuring out how much you need to save. Depending on how you're doing your move (driving, flying, renting a U-Haul) and whether or not you're going to be taking all your stuff with you or are going to need to buy new stuff. I ended up having some pretty high initial expenses because I basically moved for grad school with just clothes and books, and if I'd only had my stipend to cover it I would've been in trouble. Even before you start living off your stipend, you can do the basic outlines of a budget and figure out about how much things are going to cost you. Figure that out, as well as what initial expenses you're going to have, and that should tell you about how much you should need to save (and like others have said, I'd definitely pay off the credit card).

I went straight from undergrad into a PhD program (I'm actually at USC Annenberg, so if you'd like to PM me I'd be happy to talk to you about it more). There were parts of it that weren't as difficult as I expected it to be and then there were things that ended up being challenges that came out of nowhere. Part of the problem you have starting a PhD program without an MA (although I think this would be less of a problem if you're doing a combined MA/PhD) is that you just aren't anywhere near as familiar with the way academia works, especially at that level. There's also a huge adjustment in the amount of work and reading you're doing and how much of the work is self-directed that's much greater if you're coming straight from undergrad. It's totally do-able though, so if you know a PhD is something you want to do, I wouldn't let the fact that you don't have an MA scare you off from applying straight to PhD programs. What I might do, however, is apply to a mixture of MA, MA/PhD, and PhD programs, so that you've got options.