What lens would a photographer need for Nightclub photography, and how many flashes?

I'm planning to get a Nikon D5000 before October hopefully, and i want to get into club/rave and sports(baseball, football and soccer) photography. For sports i was thinking that i can do it for the community college i'm going to next year and get some practice there. I know sports lens are very expensive so i'll probably wait a while to get one of those, maybe next summer or something.

For nightclub photography, I have a lot of friends that throw house parties, and i can tell them if i can shoot and get some pics for my portfolio.
But will the Nikon D5000 and a 50mm f1.8 be good for night shots?
What lens would you recommend if that one isn't, and which flash would fit on a D5000, and How much would i need?

Are you trying to make money? Because I can't think of too many people who buy party pictures. Maybe the people in the photos, but if they are drunk/stoned, I doubt they'll want them. Bands won't pay much for your photos. Magazines will pay some, but competition is stiff, with many good shooters trying to break in, and they'll do an event for free, just to get a press pass.

50mm 1.8, good for parties, but you'll probably need a wider lens, 24-70 range zoom would cover it.
As for sports, a 70-200, or 100-300 would be a good starter lens.f2.8- 4 would be best, but a bit pricey.

At the very least a fast wide zoom, tamron's 17-50 f2.8 is popular with the beginning club photographer. Add an sb-700 and a good set of earplugs and you can get started.

Club photography is an interesting mix between good flash and using the funky coloured ambiant lights.