If you are expecting results like you see from some of these guys on here, you may want to save your pennies a little longer, especially for night time stuff.
At minimum you'd need a Canon XTi for a body. The lens is where you will have to spend the majority of your cash.
The lens is the most important piece of equipment you'll need to buy. The best camera body in the world will not be able to compensate for garbage glass. But, a superior lens will make a marginal body look pretty good.
If you are going to be doing night time work, even under lights, you will need lens that is a constant f2.8. You'll probably want something in a zoom.. 70-300 or so.
Count on something that's not junk to cost you around $1500 or more.
Sure, you can get a 70-300 for $300, but it's crap even in bright sunlight, unless it's tripod mounted and you are shooting completely still subjects.
I'm sure others will be along soon to tear what I just said to shreds, but that's my take on your situation.