The main joy of TV / Film Extra work is that you don't have to be a fashion mode; you apply as you are. If you haven't any teeth, if you're 85 years old, if you have a strange shaped nose - it doesn't matter. Some film or TV Show /Drama is being made in some location where they need a face or body like yours!
After all, they don't need the bees knees of good lookers for a general Charles Dickens street scene do they.
The word 'extra's' in fact is PR wise phased out. They are now known as 'Background Artistes', which I guess is more accurate.
The pay varies a lot. Basically, the more you do, or the more the face fits, the fee's can go upwards and beyond.