He has the 400d Mario
On the 400 (a crop camera) to get the equivalent of a 50mm lens you'll need a 32mm or thereabouts. The problem is the fast short canon lenses down there are quite expensive - in the £300 range and upwards), even for a sigma.
A reasonable choice might be the 35mm lens, f2 but that's still a good low light option.
https://www.google.co.uk/shopping/pr...ed=0CGYQ8wIwAA
If you're saving for a good lens I would strongly urge you to look at the 10-22mm canon lens. It's truly mighty and incredibly versatile. It is of course, not as fast as a prime lens being a zoom, and it defeats what Mario and I are trying to encourage you to do a little (zoom with your feet to learn!) BUT it's an AWESOME lens. I used one every day basically for about 3 years for skydiving. Loved that lens and would have one again in a heartbeat if I needed the functionality.