HI Yannis,
The answers haven't been really helpful. I hope my answers will give you more info.
Accommodation
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It really depends on whether you are willing to travel and how far you like to live from the city. If you are a beach person and wants to use the beach, you will be quite disappointed as the beaches in HK are quite polluted. I wouldn't want to put myself in the water. Having said that, beach areas are either the south of HK island - definitely quite expensive properties OR Sai Kung - definitely much cheaper in rent, better air and right next to the country parks. Although HK is small, traffic jam is huge. I would definitely live close to the MTR (underground) station. That's the only reliable transportation in HK. You can save the travelling time for a trip to the beach on the weekend. $$$ wise, it really depends what you are looking for and can afford. It varies a lot as previous posts said.
Eating Out
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Lots of cheap eat in HK. They are local food though. If you love the Asian food, HKD 12 can buy a bowl of noodles. A cup of coffee costs HKD 6. The only obstacle is that you may need to "point" to order food or ask other customers to help you order. Caucasians usually go to restaurants. For those restaurants serving western food, you are looking at HKD 100-150 a main course. Not cheap.
English Teacher
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There is an English (foreigner) teacher in every local school in HK to boost up the English abilities among HK students. The candidate must have an English degree though. There are quite a number of international schools in HK. You are better off to ring up these schools and start making contacts. You may be able to get a supply teacher job or coordinator type of work. Otherwise, offering private English classes is a good way to earn a living too. You will never be short of customers.
Hope this helps.