These same bosses who want to save money will deduct excessive amounts off of your electricity, heating, and water bills

Proper jarb, the more they deduct from my bills the less I'll have to pay.

These same bosses who want to save money will deduct excessive amounts off of your electricity, heating, and water bills to "make up" the fact that they think they're paying you too much money. I know because I have had this happen. As for young teachers scarping off, they risk being blacklisted if they do. This is like one of those arguments where someone says that the poor only want to scrunge off of the system however they can, when in fact only a minority do so.

I have a 6 month contract offer from a school in China. They say they can help with getting an F Visa, which is a business visa, and that Z visa's are more used for 1 year contracts. Is this correct? I was under the impression that all teachers needed a Z visa no matter how long the stay?

Lots of my colleagues are on F Visas. My lodger will be on an F Visa. You can't blame the bosses if they don't want all the hassel of obtaining Z Visa, Expert's Cerificate and so forth; especially when there are so many fly by night young FT's who are likely to scarper after a couple of months.

This is a lie. Z Visas must be obtained first, and are immediately replaced by 1 year Resident Permits as well as the working expat being issued a Foreign Experts Certificate which is the legal requirement to work as a teacher (falling under the "Wen Jiao" category of "Experts")in China. An F Visa is the gray line where you put yourself at risk at the whims of local government officials who might do a "surprise" inspection at any time to check if you are working legally or not.

Also, don't forget that if you wanted to switch jobs in China without ever having to leave the country you will need a letter of release, and if you are on an F Visa that means you will not be getting one. The money you save now for the Visa will be money that is later spent on making that extra plane trip to Hong Kong or back to your country of origin. Think to yourself: Is it worth it?