While I don't work or shoot in these kind of conditions I will second sierra's advice. If the venue is dark then a 300mm at f/5.6 on a Rebel isn't going to be fast enough or of any real use, I can't see you getting a shutter speed much higher than a second! You also won't need a focal length much longer than 70mm if you're anywhere near the bands.
What you want is a fast lens, probably the 50mm 1.8 which will allow you to keep a moderately fast shutter speed to freeze what's happening on stage. It's also inexpensive, compact and can be used for much more than shooting in clubs!
Also, are you thinking about applying to College to do photography before you even have a portfolio? I'm sorry if I sound condescending but it sounds like you're still at the stage where you simply want the longest lens rather than the most appropriate. I would also like to say that it is just about impossible to make a living from music photography, you can do it on the side as something you are passionate about, but be prepared to do more than concert shoots.
I've been saving up so I have a budget of around 300 for a lens or two, any suggestions on a specific lens? And yes I do have a portfolio, but I dont have to apply until december so I am trying to build it up some more between now and then. The colleges I'm applying for provide career services and internships, and theyre pretty big colleges so they can help me get in with big companies, even with that said, I know it not a lucrative career unless you manage to get in with large band or big magazine. I know I'll probably have to have a job on the side, but this is my passion so I'm going to pursue it.
I did suggest a lens, the Canon EF 50mm 1.8. I know it's now been reposted but I'm not sure that you realised that a 50mm 1.8 was an actual lens. It costs around $100 or £80 so it's a very good investment.
I second watching Jared Polin's earlier videos, he shares your passion for music photography and has taught me most of what I know about it. He also teaches a very important thing that you need to keep in mind, you need to be thinking about aperture as a priority when choosing a lens. A 300mm 5.6 is fun in bright sunlight but a waste of money if you're trying to shoot at f/5.6 when you can't really get past 800ISO without excessive noise.
It seems like you've got a lot to learn before December, have fun pursuing your passion.