Only those with a metal Press Badge OR permission from the racecourse to represent a press outlet are permitted to take photos for publication on a racecourse. Even if you do get permission and a Press Pass, some courses are quite sticky about where you can and can't go, whilst others (inc some of the biggest eg Ascot) are quite relaxed. Strictly speaking you should not be putting up photos anywhere inc webistes without having had that original permission; but people do of course all the time
I'm following this thread closely too as I badly need to upgrade my equipment (a Camedia), which is fine for the 'people shots' I'm mainly employed to do, inc Winners Enc, but not much good in poor light and pretty useless for track work even in bright sunlight (not that I really NEED to do that anyway, but it's good to have the option)
I've used one of the Canons that most racing photographers use, and I didn't like it at all; but I've never had enough use of it to really experiment and see what it could do. And it didn't really have a good enough lens on it so the pics tended to come out very grainy which I dislike. When I was using only an SLR camera I swore by my Nikon, and I'd always tend to favour Nikon for that reason. But as others have said, it's getting the right lens which is important
It's true that framing a shot is the most important thing though, once you have the equipment, and that's largely a matter of having a good 'eye'. My background of many years in picture research and picture editing helps there, having spent over 20 years selecting between good and p*ss-poor images...
And it's a job which you can only learn by doing, so in a sense you are a 'Pro' the moment someone pays you to go and take pics on a racecourse! - but it's a job where experience really does make all the difference, as we can see in the difference in quality between the work of forum photgraphers who do it for a living, and those who just go out and take a few pics when at the races