Been there myself. You start with photography and you look around, you read some articles, you talk to some people and then you make up your mind. At this point you still don't really understand what aperture is, how ISO works and why more mega pixel doesn't necessarily mean better camera. (Got that my Canon friends?) And then you get to this website that does lens comparison and you read that you can get this Sigma 12mm-24mm lens for a fraction of the dollars that a nikon lens would cost and you just think: YES, same lens why pay more?

Why pay more, well you will find out the hard way because if you are serious about what you are doing you will never settle for second best. You will constantly upgrading your equipment until you have the best available. So why not start with the best available at the time instead? Like in the above example, sure that Sigma will do the job and will get some photos out of your camera and if you are not shooting with a great camera like a D700 or D3 you may not even notice a big difference at the start. Then you find out what barrel distortion is and what makes a lens go sharp in corners and why there is vignetting and why there is lens flare and then you will begin to understand why some lenses cost what they cost and others are cheap as chips and sooner or later will find their resting place at the bottom of your rubbish bin.

If you are shooting interior photography and you happen to have a Nikon camera there is only one lens you should consider and that is Nikon's master piece, the mighty 14mm – 24mm 1:2.8G. You'll get one sooner or later, trust me.