There is a lot of photographers in perth, but i may see the numbers differently as i work with a lot of them.
Photographers range from the $500 - all images on a cd, find me on craigslist, to guys who are charging massive amounts of money - but produce some incredible work.
As for rent and cost of living - its pretty pricey - a cheap rent is $300 a week, typically further from the city, and in a "dodgier" area - they go up the closer you get to the city.
I havent had any trouble getting photographic work here - but i dont depend on weddings and portraits to live, i work for a newspaper, and do the ocassional wedding on the side.
If you do move - there are 3 good professional camera shops - Pra Imaging, Camera Electronic and Team Digital (along with a bunch of little overpriced ones, typically a Camera House branded store)
I am a massive fan of PRA Imaging - they have always been helpful, friendly and have looked after me.