I have an Oreck, which I love, because it is incredibly lightweight, works great, and has a great hepa filtration system. My mom gave it to me for my birthday one year though, so I don't even know how much they cost. I think they're fairly expensive.
I have never purchased a vacuum - until my mom bought me the Oreck I was using one from the '70s that had belonged to my dh's parents. It was so heavy I had thrown my back out from using it.
But a vacuum is a necessity. If you are still going to be able to pay rent, eat, and make the payments, I wouldn't worry about it too much. Like my best friend always says - if you are going to do it, then do it and enjoy it. No point in doing it and not enjoying it by stressing.