I wanted to buy canon 50D for starting a photography business , is it a good camera for shooting weddings, potraits or children?

This Nikon is actually my husbands camera and I use it..
I wanted canon from long time but he got me this Nikon because when he bought it he got a good price.
Ah, so maybe is best for me to stick with Nikon and get some great lenses..
But is it ok if I buy Sigma one? Because Nikon lenses are so so expensive
Would sigma give me a great performance?
The Sigma EX 24-70mm and 70-200mm lenses are Great. The only thing you gain for buying Nikon equivalent is VR at more than double the price.
Craig