LOL I loved the comments on the coffee. Unfortunately, you won't switch to tea because guess what? Tea will still set you back $3 and its just a tea bag chucked in a cup of water! At least the coffee takes some level of skill. Agree it is expensive but it is made by baristas (cafe style), not simply poured out of a pot. No drive through options either! $3.50 might not sound like a lot but if you have two a day at work it adds up to $35 a week!
Sydney is gorgeous and the weather is awesome but it is one of the most expensive cities in the world to live in (you can Google this!). Beats NYC, London and Paris by miles. I am Australian, living in Sydney now but lived in Toronto for 3 years with my Canadian husband.
Public transport is generally a mess. The TTC in Toronto is flawless compared to CityRail. Trains & buses also more expensive - it goes by the distance traveled not by single trip. (From memory, the TTC uses one ticket for once trip using either tram, train or bus (?). Here you'll have to purchase everything separately or get a pricey "multi-pass" ticket. Painful). Make sure you check out your transport options carefully when you decide where to live and work. If you live in the outer suburbs of the city (ie NOT downtown) it will generally take an 1hr to get into the city whether driving or train.
If you are working in Rose Bay, the closest train stations are Edgecliff and Bondi Junction. Depends on exactly where you are but you might need to walk or bus it in anyway (its a hilly area).
Looking around Rose Bay, personally, I would look at the suburbs within this area: Surry Hills, Paddington, Double Bay, Rose Bay, Bondi, Coogee, Maroubra (not further south), Randwick, Moore Park. It’ll probably be bus(es) to work.
I've always been paid weekly (SMEs). Others might be paid fortnightly (unusual) or monthly (common for larger companies). Your rent doesn't cover any utilities so budget for that as well. Water, gas & electricity is billed quarterly - prices vary with the size of your property.
I'm not sure if its worth getting a furnished apt ($850/wk is massive!). Not knowing your taste or how long you're staying (care factor), but you can get package deals for furniture here (eg. Fantastic Furniture delivers) or there's always Ikea (you'll need a car though)!